The Opal Inlay Ring is a style of ring where the opal flows along the curvature of the band, providing a sleek, smooth look.

This has become a popular style of ring due to its simple, yet effective appeal, however, there are a few attributes to this setting that you should be aware of before purchasing. 

Opal Inlay Rings feature slivers of light opal (generally from Coober Pedy, South Australia), that are glued in to small cut-aways or channels in the gold/silver band. The sections underneath the opal have been painted or coated in either black paint or black resin to provide a dark backing to the light opal slivers, thus giving the opal the appearance of Black Opal (the rarest of the Australian Opals).  Once the opal pieces are glued into the band, they are then polished down to flow with the curves of the ring.

The achieved look is definitely appealing, however due to the thickness of the opal slivers being only 1mm to 1.5mm, and with them only being glued into the setting, it is highly advisable that these rings should not be worn frequently.

If the ring is knocked/bumped against hard surfaces, due to the opal being considerably thin (and only a hardness of 6.5/10 on the Mohs scale – on par with glass), cracking/fracturing can and most likely will occur. 

Frequent immersion in moisture for inlay rings can also create issues with the adhesive breaking down. This leads to the layer of opal splintering away gradually.

In both cases, the inlay ring will need to be sent for repair, and replace the inlaid opal slice.

Because of this, Opal Inlay Rings are NOT suitable for engagement rings or wedding bands.

What we recommend, instead, is to bezel-set/rub-over a solid opal.  While the opal doesn’t completely follow the curvature of the band, using the bezel-set/rub-over technique (where the gold lip is folded over the opal to keep it safely contained) will still provide a sleek, simple and effective look for the ring, and provide a piece of jewellery that can be worn in everyday situations.

Taking care of opals is essential to maintain their natural beauty and luster. Here are simple tips to keep your opals looking stunning:

1. Gentle Cleaning: Use a soft, damp cloth to gently wipe away any dust or dirt on your opal. Avoid abrasive materials or harsh chemicals that can damage the surface.
2. Avoid Exposure: Opals are sensitive to extreme temperatures, so it’s best to avoid exposing them to direct sunlight or extreme heat for prolonged periods. Additionally, keep them away from harsh chemicals like household cleaners.
3. Remove Before Activities: While opals are relatively durable, it’s wise to remove opal jewellery before engaging in activities that could subject them to knicks or scratches. This includes activities like gardening or heavy-duty chores.
4. Proper Storage: When not wearing your opals, store them in a soft pouch or a jewellery box with compartments to prevent them from scratching against other pieces. Avoid tossing opal jewellery into a common jewellery box where they can come into contact with harder stones.
5. Avoid Immersion: Opals should not be immersed in water for extended periods, as this can lead to discoloration or damage. Remove opal rings before swimming or doing dishes to preserve their integrity.
6. Regular Inspections: Periodically inspect your opal jewellery for loose settings or signs of wear. If you notice anything unusual, take it to a professional jeweller for assessment and potential repairs.

By following these simple care tips, you can ensure that your opals remain vibrant and beautiful for years to come. Opals are not just gemstones; they are pieces of nature’s art, and proper care will help preserve their unique charm and colours.

We also have a informative read up on how to take care of your opals, feel free to read more.

Opal rings are special—they’re not just jewellery; they’re like tiny pieces of nature’s art. The beautiful colours inside these gems tell stories of elegance, uniqueness, and timeless beauty. It doesn’t matter if you know a lot about gemstones or if you’re buying jewellery for the first time; exploring the world of opal rings is like going on an adventure.

Opal rings come in different types, each with its own charm:

• White Opals: These are classic and timeless. They have a light colour that’s a perfect background for the amazing colours that dance on the gem.
• Black Opals: These are rare and luxurious. They have a dark colour that makes the vivid colours on the gem’s surface even more intense.
• Boulder Opals: These are earthy and captivating. Boulder opals in rings show off unique colours against their natural ironstone host rock.
• Crystal Opals: These are elegant and see-through. Crystal opals in rings let the colours shine through a clear or slightly see-through body.

Choosing Your Opal Ring

Picking the perfect opal ring is easy when you think about a few things:

• Setting Styles: Do you like gold or silver? Gold makes the ring warm, while silver gives it a more modern look.
• Cut Choices: Opals can be cut in different ways. Choose a cut that matches your style, whether it’s a classic oval, round, or something more unique.
• Opal Varieties: Every opal is a bit different. Get to know the type in your ring, and you’ll appreciate the special charm each one has.
  
  Shop with confidence – Browse our wide range now!

Taking Care of Your Opal Ring

Ensure your opal ring retains its allure with these care tips:

• Avoid Harsh Chemicals: Steer clear of strong chemicals to preserve the opal’s lustre.
• Protect During Activities: Remove the ring before engaging in activities that may cause impacts or scratches.
• Gentle Cleaning: Use a soft cloth to clean your opal ring gently.

Read our guide to taking care of your Opal Rings

From selecting the right opal variety to understanding cuts and settings, each element contributes to the timeless charm of these rings. From 50+ years of knowledge and experience Opals Down Under is lucky enough to have a unique range of opals rings, so be sure to check them out online here.

We also have an extensive range of online posts that provide more in-depth knowledge about the world of opals!

Feel free to take a look.

Embracing the Magic of Crystals: A Beginner’s Journey

Welcome to the world of crystals, where ancient wisdom meets modern fascination. As a beginner, the realm of gemstones may seem overwhelming, but fear not! This essential guide offers practical tips and advice to nurture your precious crystals. Let us embark on a journey to unravel the mysteries of choosing, cleansing, and using crystals, empowering you to connect with their healing energies.

Choosing Your Crystal Companions

1. Follow Your Intuition
   • When choosing crystals, trust your intuition. Allow your instincts to guide you toward the gemstones that resonate with you. Whether it’s the color, shape, or feeling you get when holding a crystal, your intuition will lead you to the right ones.
2. Research Crystal Meanings
   • Familiarize yourself with the meanings and properties of different crystals. Books, online resources, and reputable crystal guides can provide valuable insights into the unique qualities of each gemstone. Understanding their energies will help you select the crystals aligned with your intentions.

Nurturing Your Crystal Treasures

1. Cleansing Your Crystals
   • Crystals absorb energy from their surroundings, and regular cleansing is essential to maintain their vitality. Use one of the following methods to cleanse your gemstones:
   • Water: Rinse your crystals under cool running water, imagining the negative energies being washed away.
   • Smudging: Pass your crystals through the smoke of sage or palo santo to purify them.
   • Earth: Bury your crystals in a bowl of soil or natural salt to ground and cleanse them.
   • Full Moonlight: Place your crystals under the light of the full moon overnight to recharge their energy.
2. Setting Intentions
   • Crystals are powerful amplifiers of energy and intention. Before using a crystal, set a clear and positive intention for its purpose. Visualise your desires while holding the crystal, infusing it with your intentions.

Using Crystals in Your Daily Life

1. Meditation and Mindfulness
   • Integrate crystals into your meditation practice to deepen your connection with yourself and the universe. Hold a crystal that aligns with your meditation goals or place it nearby to enhance your focus and relaxation.
2. Carrying Crystals with You
   • Keep small crystals in your pocket or wear them as jewelry to carry their energies with you throughout the day. For example, Amethyst can support calmness during stressful moments, while Rose Quartz fosters self-love and compassion.

Your Guide to Crystal Enlightenment

At Opals Down Under, we cherish the transformative power of crystals and are here to guide beginners on their crystal journey. Our passion for gemstones and their healing properties fuels our commitment to offer expert advice and a diverse selection of crystals. Begin your exploration with confidence and let the magic of crystals enrich your life.

Discovering the Magic of Crystal Meanings

Crystals have captivated humanity for centuries with their mystical allure and inherent energies. In this comprehensive guide, we delve into the enchanting world of crystal meanings and uncover the unique qualities each gemstone possesses. Explore how crystals can be harnessed for various purposes, from promoting tranquility to stimulating creativity, and embark on a journey of self-discovery with the wisdom of crystals.

A Journey Through Crystal Meanings

1. Amethyst: The Stone of Spiritual Protection and Intuition
   • Amethyst is renowned for its ability to foster spiritual growth and intuition. Embrace its calming energies to ease stress and promote inner peace. Meditate with Amethyst to enhance spiritual awareness and connect with higher consciousness.
2. Rose Quartz: The Gem of Love and Emotional Healing
   • Rose Quartz resonates with unconditional love and emotional healing. Use this nurturing crystal to attract love and enhance self-acceptance. Allow Rose Quartz to heal emotional wounds and cultivate compassion in your heart.
3. Citrine: The Crystal of Abundance and Positive Energy
   • Citrine radiates warmth and positivity, attracting abundance and success. Place Citrine in your workspace to enhance creativity and manifest your desires. Its vibrant energy uplifts the spirit and invites prosperity into your life.
4. Clear Quartz: The Master Healer and Amplifier
   • As the master healer, Clear Quartz enhances the energy of other crystals and intentions. Program Clear Quartz with your goals and intentions to amplify their manifestation. Its versatility makes it an indispensable crystal for any collection.

Crystal Uses in Everyday Life

1. Meditation and Mindfulness
   • Crystals play a significant role in meditation, facilitating relaxation and focus. Choose crystals that resonate with your meditation goals, such as Amethyst for spiritual connection or Selenite for mental clarity. Hold or place the crystal near you during meditation to enhance your practice.
2. Chakra Balancing and Alignment
   • Crystals are used in chakra balancing to align and cleanse the body’s energy centers. Select crystals that correspond to each chakra, such as Lapis Lazuli for the Third Eye chakra or Rose Quartz for the Heart chakra. Place the crystals on the corresponding chakra points during meditation or energy work.
3. Enhancing Energy and Well-Being
   • Crystals can positively influence your energy field and overall well-being. Carry or wear crystals like Citrine or Carnelian to boost vitality and confidence. Place crystals in your living space to create a harmonious and energetically balanced environment.

Opals Down Under: Your Gateway to the Crystal Realm

At Opals Down Under, we celebrate the beauty and power of crystals, offering a diverse selection of high-quality gemstones. Our expert team is passionate about guiding you through the enchanting world of crystal meanings and their myriad uses. Explore our collection in-store, and let the wisdom of crystals enrich your life’s journey.

A relatively soft stone (ranking 6.5/10 on the Mohs Hardness Scale), Australian Opal has a hardness that is relative to glass, so it is important to treat your Australian Opal with care to avoid any potential damage.  

If there is a chance your opal could be in a situation where it will be scratched or fractured (for example, working out at the gym, instances where heavy lifting is occurring, gardening etc), then it is highly recommended that you remove your opal jewellery to avoid any damage.

It is a common misconception that natural Australian Opals can be damaged by being immersed in water, when in fact this is incorrect. Solid Australian Opals are non-porous, and will not absorb moisture.  The majority of precious opal will contain approximately 3-5% moisture.  However, water damage can occur to Doublet Opal and Triplet Opal as they are laminated pieces – in which immersion in water frequently will cause the glue holding the layers of the Doublet or Triplet together will begin to break down.  It is recommended to avoid exposing Solid Australian Opal to extremely high (and low) temperatures as this may cause internal fracturing or cracking.

To clean your solid Australian Opal – it should be cleaned gently with mild detergent in warm water and a soft toothbrush or cloth.  You can also use a small amount of ammonia, diluted in water, to achieve this result.  It is NOT recommended to clean your opal in an Ultrasonic cleaner, as the intense vibrations can causing cracking/fracturing.

To store your solid Australian Opal – if you ever need to store your solid Australian Opal away in a safe place or a drawer, simply place it in a padded bag (or display box) for protection.  In the case of longer periods of storage (such as in a safe or safety deposit box), seal the solid Australian Opal in a plastic lock-seal bag with a moistened cotton ball to prevent any potential drying/dehydration which can lead to internal fracturing.

FAQ :  What are opal fossils? Where are black opal fossils found? What does opalized / opalised mean?

Lightning Ridge – Black Opal Fossils

Only one place on Earth produces black opal fossils – Lightning Ridge in northern New South Wales, Australia. Lightning Ridge is the only opal field in Australia with fossils of diverse land-living organisms – pinecones and platypuses, microscopic protozoans and gigantic dinosaurs. The fossils are usually exact replicas of plant, shell or bone material, and at times they are comprised of gem quality black opal, which is as valuable as diamonds and more beautiful.

Black opal fossils which may be found at Lightning Ridge include remnants of ancient plants, mussels, snails, crustaceans, fish, turtles, plesiosaurs, crocodiles, pterosaurs, dinosaurs, birds, and mammals. 110 million years ago the supercontinent Gondwana was a wilderness of forests of pines, ferns and palms separated by tracts of shallow sea. Dinosaurs and their relatives dominated this landscape, as well as our rare and tiny mammal ancestors. Near the edge of this ancient continent, fragments of the remains of these animals accumulated in the sands of the inland sea. Today deposits at Lightning Ridge in northern New South Wales yield some of the rarest, most beautiful and precious fossils in the world.

Lightning Ridge fossils are three-dimensional replicas of ancient organic objects, transposed into non-precious potch or precious opal. In those that are pseudomorphs, the silica has filled a simple cavity or void, like jelly in a mould, so that only the basic shape and perhaps the surface texture is preserved. However, many specimens are replacement fossils, in which intricate internal structures have been preserved by chemical alteration before the cavity was filled by the silica solution.

Most specimens at the Ridge are a combination of pseudomorph and replacement fossils. Although the transformation to silica has destroyed biomolecular evidence, marrow tissue, blood vessels, capillaries and nerve channels may be perfectly preserved. If the potch is transparent, these features are clearly visible below the surface in opalised bones. A surprising aspect is the opalisation of delicate materials like leaves and even dinosaur skin. Many pieces resemble coprolites, reptilian armour scutes or heavy scales; very occasionally, bone specimens seem to show remnants of tendons or cartilage.

This outstanding quality of preservation is partly because the opal-dirt is extremely fine-grained and an ideal casting medium. Kaolinite, smectite, and illite produce the putty-like properties of the opal clay, the smectite making it plastic and malleable.

Most opal fossils found at the Ridge consist of potch (colourless opal), therefore any fossils with colour are rare and valuable. Many fossils are damaged by machinery during excavation, as pick and shovel based operations are giving way to machine-driven excavations. Removing fossil specimens can be a delicate operation, and colourless fossil specimens are largely ignored by miners searching for colour.

South Australian Fossils

The opal fossils of the South Australian opal fields are both jewels of science and beautiful gems. The Eromanga Sea that covered the interior of Australia 100-120 million years ago was rich in marine life. Ichthyosaurs, plesiosaurs, fish, sharks, ammonites and belemnites swam in the open water. Slow-moving and sedentary animals, such as starfish, crinoids, cockles, mussels, snails and tube-worms lived on the seafloor.

Only those bones and shells that became trapped in seafloor sediment had a chance of becoming fossils. Some were replaced by clear silica, and others by precious opal.

One area which yields a vast resource of opal fossils is Moon Plain, approximately 35km from Coober Pedy in South Australia’s outback. Once part of a vast inland sea which covered most of Australia, Moon Plain once teemed with marine life, but is now a wonderland for palaeontologists. South Australia has the best cold water cretaceous marine deposits in the world, and it is difficult to imagine the extreme freezing temperatures of millions of years ago compared with today’s scorching heat.

Sources :

• “Black Opal Fossils of Lightning Ridge”, Elizabeth & Robert Smith, Kangaroo Press, 1999.
• Origin Energy Fossil Gallery
• Australian Museum Online

The following outside resources are available for download in PDF format and require Adobe Reader.

To download a file, please right-click on the link and select ‘Save Target As’.

• OPAL Mineral Information Leaflet – QLD Govt. Dept. of Mines & Energy – October 2000.
• Opal Minfact – NSW Department of Primary Industries – January 2000.
• Strategic Assessment of the Australian Opal Industry – by David Horton (Opal Horizon) May 2001.
• Australian Sedimentary Opal – Why is Australia Unique? – by David Horton December 2002.
• What you should know about buying opal – Jewellery Association of Australia
• The origin of precious opal – by Byron Deveson
• Opal mining in Lightning ridge, review of environmental factors – NSW Dept. of Primary Industries
• Mining at Lightning Ridge – NSW Dept. of Mineral Resources

Safety on the opal fields

Australia produces over 90 per cent of the world’s precious opal, and more than half comes from NSW opal fields. The major opal-producing areas in NSW are Lightning Ridge and White Cliffs. Visitors may fossick or “spec” for opal on a field provided they have first obtained permission of the landowner or leaseholder. If the area is subject to a registered mineral claim, a visitor must also seek permission from the claimholder. Please see section below on “The Mining Act 1992”.

A warning

A fifteen year old boy was helping in his father’s underground opal mine when he fell six metres down an internal vertical shaft and suffered a broken leg and bruised back. He was helping his uncle and father who were mining an exploration drive about 10 metres below the surface. They had deliberately holed into the small old workings of the adjacent mine so that they could evaluate the ground ahead of them. They had one porta flood light between them that was powered by a surface generator. The electric cable to their light only stretched two metres into the old workings, but they saw what they wanted to see and the two adults returned through the opening. Unknown to the adults, the son, who was at the rear, suddenly decided to explore one of the old drives, even though he had no light to see where he was going. In the darkness, he stepped into a small unprotected six metre deep vertical internal shaft in the drive floor and fell to the bottom. He was immobilised by his injury. The rescuers gained access to where he was through an adjoining shaft.

Please exercise extreme caution whilst mining or visiting a mining field;

• Do not allow inexperienced people alone in underground mine workings
• All persons who are taken underground must be instructed and/or supervised to an appropriate level of understanding.
• Every person underground should carry a light.
• Unfamiliar workings must be considered to be dangerous and must be secured against casual entry.
• Never position a winze in the middle of a drive or cross-cut.
• School children on holidays in a work situation need constant supervision.

Fossick in Safety

Established opal fields may be good places for fossicking, but there are many hidden dangers. Children are especially vulnerable, and need to be kept under close supervision at all times. Fossickers should first make their presence known to any miners in the area. Remember heavy mining and earthmoving equipment is used on opal fields, and can operate without warning. Self-tippers and blowers bring dirt to the surface of claims from underground , often working unattended.

Shafts, drill holes and open cuts may pose a serious danger to young children. Drill holes in particular – about the width of a child’s foot – are extremely dangerous. Shafts and drill holes may be full of water and may be camouflaged by vegetation growth. Old shafts or drill holes may be in a dangerous state, with collapsed collars or protected only by rotten timber or rusted sheets of iron.

Fossickers are warned against entering old underground workings without the benefit of experienced and competent miners to assist. Many dangers exist such as unstable ground, stale air and lack of oxygen, unprotected openings underneath and holes full of water. Seek help before entering old mines. Fossicking may only take place to a depth of one metre and all holes dug must be refilled. Fossickers are also warned against entering old open cuts or costains and especially warned against fossicking into the sides of excavations which may cave in unexpectedly. Large stockpiles of dirt may also collapse unexpectedly particularly if they are undercut.

When fossicking wear strong clothing, a hat and shoes. If you are fossicking alone tell someone where you are going in case you get into difficulties. In hot weather carry plenty of water. A first aid kit is always advisable. Avoid snakes; don’t try to handle or kill them. Please note too that transport can be a problem in these areas, not only because of the distances involved, but also because of the heat. A car will be needed to visit the main fields.

Equipment for Fossicking

You will need, as a minimum:

• Pick;
• Shovels;
• Pans;
• Sieves;
• A pair of tweezers and a hand lens (x8 or x10) to help identify your find;
• Hat;
• Insect repellent;
• Boots;
• Small collecting jars.

The Mining Act 1992

Under section 12 of the Mining Act 1992, “A person must not fossick for minerals on any land that is the subject of an authority, a mineral claim or an opal prospecting licence except wih the consent of the holder of the authority, claim or licence.”

Fossickers must not use any explosives or power-operated equipment, drill or excavate to a depth of more than one metre, damage or remove any bushrock, or remove more than 20 grams of gemstones during any single period of 48 hours. A person who wishes to do more than fossicking, for example prospect and/or mine for opal, must have a licence under the Mining Act 1992. This can be an opal prospecting licence, an exploration licence, a mining lease or a mineral claim.

In traditional opal mining areas in NSW such as in Lightning Ridge and White Cliffs, prospecting for opal is mostly carried out under a mineral claim or an opal prospecting licence, if such is available. Other States may have different requirements. The maximum area allowed in NSW under a mineral claim is two hectares but within the Lightning Ridge Mineral Claims District and the White Cliffs Mineral Claims District, where special rules apply, a mineral claim is restricted to 1/4 of a hectare (i.e. 2,500 square metres).

A mineral claim authorises the holder to prospect as well as mine and a person is restricted to two claims in each District. Opal Prospecting Licences are granted over much larger areas than those granted under mineral claims but are purely for prospecting and do not authorise mining. An Opal Prospecting Licence can only be granted over lands defined as an “Opal Prospecting Block” within an area designated under the Mining Act as an “Opal Prospecting Area”. There are a number of Opal Prospecting Areas in the Lightning Ridge and White Cliffs Mineral Claims Districts.

For further information on the various titles available, the rights and duties of holders of titles and the policies that apply, contact the Department of Mineral Resources or the Mining Registrar at Lightning Ridge, or the Mining Registrar at Broken Hill.

Code of Conduct

The New South Wales opal fields are located on pastoral leases, which are still used for farming purposes. Please recognise that while visiting the fields you are a guest on a working cattle or sheep station, and respect the owner’s requirements. Do not take dogs to the fields, leave all gates as you find them, and take away your garbage. Visitors are requested to read a copy of the full code of conduct, which can be obtained from Department of Mineral Resources offices.

For more Information

Further reading:

• Opals in New South Wales, Department of Mineral Resources.
• The Mining Act 1992 (New South Wales)
• Mine Health and Safety Act 2004 (New South Wales)
• Code of conduct on the opal fields, Department of Mineral Resources.
• Gemstones in Australia, Australian Gemstone Industry Council, 1993.
• Australian precious opal: A guide book for professionals, Andrew Cody Pty Ltd, 1991.
• Australian opals and gemstones, Australian Gem Industry Association, 1987.

Places to go for information

The Department of Mineral Resources
Information Counter
29-57 Christie Street
St Leonards 2065
(PO Box 536, St Leonards NSW 1590)

Telephone: (02) 9901 8269 begin_of_the_skype_highlighting              (02) 9901 8269      end_of_the_skype_highlighting
Fax: (02) 9901 8247

OR 

Lot 60
Morilla Street
(PO Box 314)
Lightning Ridge 2834

Telephone: (02) 6829 0678 begin_of_the_skype_highlighting              (02) 6829 0678      end_of_the_skype_highlighting / 0824
Fax: (02) 6829 0825

Sources: 

• NSW Dept. of Primary Industries

A new era for opal nomenclature

Anthony Smallwood FGAA, GG
Chairman, G.A.A. Opal Nomenclature Sub-committee

Abstract

Opal is a relatively common mineral species that is found in many locations world wide. For many years a reason for the spectacular phenomenon known as play-of-colour, as seen in precious opal, remained a well hidden secret. It was not until the 1960s that Australian scientists working at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) used a new instrument now known as the electron microscope to reveal the inner structure of opal and how this is responsible for generating the play of colour of precious opal.

Opal often was referred to as a ‘semi-precious gemstone’, until unique Australian black opal was discovered and successfully marketed. Today, all varieties of precious opal, which are mined in the Australian states of New South Wales, South Australia and Queensland, support a $A500 million per year industry.

One problem that the opal industry has been required to face, however, is how does one describe a gemstone that occurs both with and without a play-of-colour, in almost every colour of the rainbow, in every tone of lightness and darkness from black to white, and in every degree of transparency from opaque to perfectly transparent. Also this unique gemstone displays differences in mineralogy that reflect the varying geological environments in which it forms.

The opal nomenclature that follows is a result of three years of striving within Australia’s opal industry to achieve co-operation and to formulate a nomenclature for opal which is accepted uniformly throughout the industry.

Introduction

For many years the terminology and nomenclature used to describe opal has been widely discussed and debated by gemmologists and those members of the gem and jewellery industry who have an interest in this gemstone. Aspects of this long-running discussion can be seen in the long list of papers published throughout the forty year history of The Australian Gemmologist. But, how to best describe opal (arguably the most beautiful of gemstones) has been a contentious and difficult issue for a very long time — and may well remain so for some time to come. However, as a consequence of factors such as: growing international and local awareness of opal as a major Australian resource; the emergence world-wide of a real desire to standardise all terminology related to gemstones; and the ever growing number of synthetics and imitations that are appearing in world markets; it has became necessary to agree on some well based concepts of how a unique gem material, such as opal, should be described. It was late in 1993 that the Australian Gemstone Industry Council requested the then President of The Gemmological Association of Australia (GAA), Grahame Brown, to initiate investigations into the possibility of establishing a uniformly accepted nomenclature for opal. After a short time, a working sub-committee of the GAA was formed that consisted of representatives of The Gemmological Association of Australia, the Australian Gem Industry Association (AGIA), and the Lightning Ridge Miners Association (LRMA). Now, after three years of discussion, correspondence, and a plethora of drafted documents, and what seemed to be a never ending train of ideas and criticisms, a final draft nomenclature has been agreed-to, ratified, published, and is presented in this paper.

The Australian Gemstone Industry Council (AGIC) has accepted this nomenclature in its final draft, as has the GAA’s 1996 and 1997 Federal Conferences in Tasmania and Perth — albeit with one or two small amendments to the final draft. Now the AGIC hopes to actively progress production of a full colour publication and video on this opal nomenclature for distribution on a world-wide basis over the next twelve months. As Chairman of the GAA’s Opal Nomenclature sub-committee I would like to express my gratitude to Jack Townsend (South Australia), Kathy Endor (Queensland) and Andrew Cody (Victoria) for their untiring efforts and fruitful discussions. Also, this author wishes to express his appreciation for the work and constant liaison of the AGIA sub-committee members Glenn McKean, Drago Panich, Peter Sherman, and Peter Evans, as well as the generous support and hospitality offered by members of the LRMA — in particular Joe Schellnegger, Maxine O’Brien, and Frank Palmer.

I would encourage all members of the GAA to read and to use this nomenclature — in their every day activities, such as buying and selling, and in scientific correspondence and lectures. This nomenclature remains, according to GAA Past President Ronnie Bauer and the AGIA’s Andrew Cody, a ‘living document’. As time passes there will be, no doubt, more discussion and criticism of this nomenclature.This will be most welcome, as are any questions — all of which may be forwarded in writing to the GAA’s Opal Nomenclature Sub-committee either care of the Federal Office of the GAA at P.O. Box A791, Sydney South NSW 1235, or direct to the author at P.O. Box 692, Sutherland NSW 2232.

The nomenclature and classification of opal, that follows, is reproduced, verbatim, from the Resolutions of the Federal Council of the Gemmological Association of Australia (dated 17th May, 1997).

Opal Nomenclature and Classification

Introduction

Opal is Australia’s National Gemstone. Australia produces 95% of the world’s natural precious opal supply. This nomenclature encompasses all types and varieties of opal to provide a standardisation of terminology but does not establish any valuation methodology.

The Australian Gemstone Industry Council Inc., in collaboration with the Australian Gem Industry Association Ltd., the Gemmological Association of Australia Ltd., the Lightning Ridge Miners Association Ltd. And the Jewellers Association of Australia Ltd., has produced the following nomenclature for the classification of opal.

Opal Classification

Opal is a gemstone consisting of hydrated amorphous silica with the chemical formula SiO2.nH2O. There are two basic forms of opal described by visual appearance.

Precious Opal – is opal which exhibits the phenomenon known as play-of-colour, produced by the diffraction of white light through a micro-structure of orderly arrayed silica spheres to produce changing spectral hues.

Common Opal and Potch – is opal which does not exhibit a play-of-colour. The distinction between common opal and potch is based on formation and structure. Potch is structurally similar to precious opal but has a disorderly arrangement of silica spheres. Common opal shows some degree of micro crystallinity.

Types of Natural Opal

Natural opal is opal which has not been treated or enhanced in any way other than by cutting and polishing. There are three types of natural opal, with varieties described by the two characteristics of body tone and transparency.

Natural Opal Type 1 – is opal presented in one piece in its natural state apart from cutting or polishing and is of substantially homogenous chemical composition.

Natural Opal Type 2 – is opal presented in one piece where the opal is naturally attached to the host rock in which it was formed and the host rock is of a different chemical composition. This opal is commonly known as boulder opal.

Natural Opal Type 3 – is opal presented in one piece where the opal is intimately diffused as infillings of pores or holes or between grains of the host rock in which it was formed. This opal is commonly known as matrix opal.

Varieties of Natural Opal

The variety of natural opal is determined by the two characteristics of body tone and transparency.

Body Tone

The body tone of an opal is different to the play-of-colour displayed in precious opal. There are three varieties of natural opal based on body tone. Body tone refers to the relative darkness or lightness of the opal when ignoring the play-of-colour.

Black Opal – is the family of opal which shows a play-of-colour within or on a black body tone by reference to the AGIA Body Tone Chart N1, N2, N3 and N4 when viewed face up.

Dark Opal – is the family of opal which shows a play-of-colour within or on a dark body tone by reference to the AGIA Body Tone Chart N5, N6 when viewed face up.

Light Opal – is the family of opal which shows a play-of-colour within or on a light body tone by reference to the AGIA Body Tone chart N7, N8 or N9 when viewed face up. The N9 category is referred to as white opal.

Opal with a distinct coloured body (such as yellow, orange, red or brown) should be classified as black, dark or light opal by reference to the AGIA Body Tone Chart with a notation stating its colour hue.

Australian opal body tone chart indicator

Transparency

Opal shows all forms of diaphaneity and ranges from transparent to opaque. Natural precious opal which is transparent to semi-transparent is known as crystal opal. Crystal opal can have either a black, dark or light body colour tone. The term “crystal” in this context refers to appearance not a crystalline structure.

Opal Treatments

Opal can be subjected to various types of treatment. Present CIBJO guidelines state that any method of treatment other than standard cutting and polishing must be disclosed and the process used specified on all invoices, advertising and commercial documents. Types of treatments include colour enhancement, heating, painting, dying, resins and waxes, oiling or any application of chemicals. Opal is treated to change its natural appearance, structure or durability. Opal is colour enhanced in opal inlay jewellery where usually a thin solid crystal opal has black paint or glue applied or set above black painted jewellery.

Composite Natural Opal

Composite natural opal consists of natural opal laminates, manually cemented or attached to another material. The opal component is natural opal. There are three main forms of composite opal:

Doublet Opals – are a composition of two pieces where a slice of natural opal is cemented to a dark base material.

Triplet Opals – are a composition of three pieces where a thin slice of natural opal is cemented to a dark base material and a transparent top layer, usually of quartz or glass.

Mosaic and Chip Opals – are a composition of small flat or irregularly shaped pieces of natural opal cemented as a mosaic tile on a dark base material or encompassed in a resin.

Synthetic Opal

Synthetic Opal is material which has essentially the same chemical composition and physical structure as natural opal but has been made by laboratory or industrial process. Synthetic composites exist as synthetic doublets, triplets or mosaics and must be disclosed as synthetic composites.

Imitation Opal

Imitation Opal is material which imitates the play-of-colour of natural opal, but does not have the same physical and chemical structure or gemmological constants as natural opal.

Classification Reports

Classification reports for the following types of opal should include these details:

Natural Opal

1. Type of opal
2. Variety of opal as Black opal, Dark opal or Light opal with a body classification from N1 (Black) to N9 (White) based on the AGIA Body Tone Chart.
3. Transparency as opaque, translucent or transparent. Note if it is crystal opal.
4. Weight and dimensions

Treated Opal

1. Type of opal
2. Variety of opal as Black, Dark or Light opal
3. Transparency as opaque, translucent or transparent. Note if it is crystal opal.
4. Type of Treatment and process if known
5. Weight and dimensions

Composite Opal

1. Type of composite as doublet, triplet, mosaic or chip opal
2. Treatment process, where relevant
3. Dimensions

Synthetic and Imitation

1. Gemmological category including manufacturer (if known)
2. Description (Body Tone)
3. If composite, mention type as doublet, triplet, mosaic or chip
4. Weight and dimensions, only dimensions if composite

Origin

Any indication of the origin of opal by the use of geographical location should not be used unless it is qualified as an indication of the type of locality only as recommended by the International Confederation of Jewellery, Silverware, Diamonds, Pearls and Stones (CIBJO) such as Lightning Ridge type black opal.

How to Use the New Opal Nomenclature

This nomenclature for opal has been designed for use throughout the gemstone and jewellery industry, not only in Australia but internationally. While preparing this nomenclature, the sub-committee has been cognisant of conventions of international trade organisations, such as the International Confederation of Jewellery, Silverware, diamonds, pearls and stones (CIBJO), the International Colored Gemstone Association (ICA), as well as the linguistic problems associated with different languages and the differing connotations these languages may place on an internationally acceptable nomenclature.

This new nomenclature has not been designed to force any changes to the various colloquial terms used to describe opal in Australia, or indeed in countries overseas such as Mexico. Colourful language, Australian colloquial terms for opal, and terms that have been a part of the Australian scene for hundreds of years have added significantly to the mystique and folklore of everyday language used on the opal mining fields. Expressive local terms and older historical terms always will exist in the opal miner’s vocabulary. These will remain to have their rightful place in our gemstone history and in the tale-telling for years to come.

The purpose of the nomenclature, therefore, remains to provide a basic description of the gemstone we all prize and know as opal. This nomenclature is for everyone to use and understand. Simple descriptive terms, that can be used by the majority of people, from the customer to the scientist, have been chosen. These provide the gemstone industry as a whole with a logical and unbiased way of grading and evaluating opal. However, simple terms do become difficult when the many different types, formations, pseudomorphic fossil replacements, mineralogical types, and geological occurrences of Australian opal are considered.

Having said that, there are a few items of terminology which it is hoped this nomenclature will remove from common usage. In particular, the terms that have been deliberately removed, due to the linguistic problems they create, are ‘semi-black’, ‘grey’, and ‘solid’.

To begin with the first part of the nomenclature, mention is made of precious opal, potch and common opal. The best way of determining the difference between these is to observe whether or not the opal you are viewing shows the phenomenon which we all know as play-of-colour. It is possession of this optical phenomenon for which opal is most prized. The differentiation between these basic forms of opal is therefore quite simple. If the opal displays a play-of-colour it is termed precious opal. If a play-of-colour is not displayed, then the opal is either common or potch opal. While it is recognised that the term precious is neither a scientific nor gemmological term, it is retained in this nomenclature for simplicity, and with the intention of further enhancing the value of opal as a gemstone by removing it from any historical association with ‘semi-precious’ gemstones.

In an attempt at keeping the nomenclature simple to use, the terms common opal and potch opal have not been separated. It must be recognised, however, that there are distinct mineralogical differences between potch and common opal. (Jones & Segnit, 1971).

The term ‘solid’ has been removed from opal terminology, for the simple reason that all types of opal are essentially solid from a scientific point of view. That is, opal does not exist naturally either as a liquid or a gas. ‘Solid’ has been replaced by the gemmological term natural opal. Correlating with this use is the recommendation that when describing doublets and triplets that the term composite be used instead of ‘assembled’. This also is the terminology currently recommended by CIBJO.

Essentially there are three types or forms of natural opal, which are termed simply opal, boulder opal and matrix opal. Perhaps the most contentious issue in the nomenclature concerned introduction of the term body tone, to describe the comparative lightness or darkness of an opal as distinct from its play-of-colour. Technically, it would have been best just to have two types of ‘body tone’ — either ‘black or white’ or just ‘light or dark’. However, the sub-committee rightly decided not to attempt to change too much of the terminology that had been in common use for over a hundred years. So, inclusion of the term black opal was considered to be an imperative. Following much discussion the term body tone was included in the nomenclature to describe the comparative lightness or darkness of opal — irrespective of its play-of-colour. The term tone, which is used by colour science, is in agreement with terminology used internationally to describe the lightness or darkness of particular hues or colours.

The Scale of Body Tone ranges from N1 to N9. The prefix “N” reflects the neutral tone of this scale.The steps in the scale of body tone, which are arranged to indicate approximately equal decreases of darkness, are difficult to reproduce accurately on the printed page. A rough gauge can be obtained by printing this scale with the assistance of a good computer and a quality laser or ink jet printer.

After examining current industry standards, the N4 category was decided to be the cut-off point for black opal. The AGIA is currently attempting to produce a scale of body tone, using commercially available computer scanning devices and suitable software. However, at the time of publishing this paper, this scale is not yet available. The current reference, used by the Lightning Ridge Miners Association, is the neutral tone scale specified in the American Geological Society’s Rock-colour chart † . This has proved to be a good guide, for in most instances it will be possible to correlate the different ‘tone scales’ into a simple and repeatable system. An acceptable descriptive term was sought also to describe those opals that have distinct body colours or hues, such as those displayed by both Mexican fire opal and honey opal from Lightning Ridge — considerable amounts of which consists of common or potch opal. However, as an acceptable all round term could not be found to describe these opals, the committee decided to describe them by determining their body tone/s, their primary and secondary body colour/s or hues, and their transparency.

To determine the body tone of an opal, then, one examines the piece of opal, face-up, and determines (by visual comparison) its position in the scale of body tone.

• If the tone of the opal appears darker than N4, then the opal may be classified a black opal. Consequently, any opal with a body tone darker than N4, irrespective of hue, can correctly be termed black opal. Some boulder opal possesses this body tone, so it is very correctly termed black boulder opal. It is also appreciated that some very dark red Mexican-type opals would have dark enough body tones to be categorised as black opal.
• If the opal is lighter than N4, and its tone corresponds to N5 or N6 on the scale of body tone, then it is classified as dark opal. If, in addition, this opal has a decided hue colour, it is additionally classified as, for example, a dark blue opal.
• If, on the other hand, the tone of the opal corresponds to N7, or lighter, it is classified as light opal. If this light opal also has a hue, then it is termed, for example, a light yellow opal.

When to term an opal a crystal opal also provided considerable discussion. The key to classification as crystal opal is really the transparency of the opal. Perhaps a better term would have been ‘transparent opal’; but any change in terminology from crystal to ‘transparent’ may take many many years to progress. The obvious problem with the term crystal opal is, of course, the basic fact that that opal has no crystal structure. Again the sub-committee decided that it was unwise to change a term that had been in common use for so many years. The sub-committee further believes that overseas gemmological communities may yet force a change in this usage, if strict terminology is ever to be implemented.

The range of transparency considered acceptable for defining crystal opal (transparent to semi-transparent) was taken straight from Robert Webster’s discussion on transparency in his world-renowned textbook Gems. The committee decided that transparency did not need to be re-defined in the nomenclature; but just stated as a classifying category.

To grade the transparency of an opal with the nomenclature, how transparent the opal is must be determined. If the opal is only translucent, then it is not termed crystal opal. It should be remembered that in some instances the play-of-colour of crystal opal will be so strong or brilliant that assessment of transparency, by the normal ‘read-through’ criterion, may not be possible as the opal can not be ‘read-through’. When this occurs the best test of transparency would be to ‘look-through’ the opal with transmitted light. If transparency exists then this will be readily apparent. If the material remains only translucent, then it is correctly labelled as light opal. It is hoped that future scientific advances may yield a better and more accurate method of assessing transparency.

A note also should be made concerning the removal of the term ‘jelly’ opal. The basic facts are that due to the extreme transparency of this opal it becomes a type of lower quality crystal opal that displays subdued low quality play-of-colour. In spite of any restriction applied by this terminology the term ‘jelly’ opal will probably remain in colloquial use for many years to come.

The description of composite stones requires only a small change in nomenclature. Instead of these opals being described as ‘opal doublets’ or ‘opal triplets’, the nomenclature emphasises their composite nature by terming these doublet opals and triplet opal s. In this terminology, which emphasises the composite nature of these opals, it is the first word of the term that precisely identifies the material.

The rest of the nomenclature discusses opal treatments, synthetics and imitations. These are not associated with the descriptive nomenclature for natural opals, but have been included to complete the nomenclature. These descriptions are in accordance with the latest edition of CIBJO’s Classification of materials and Rules of application for diamonds, gemstones, and pearls.

Acknowledgements

The author wishes to thank Peter Sherman and Frank Palmer for providing specimens for examination. Rudy Weber’s photographic talents are gratefully acknowledged.

Sources : 

• Australian Opal & Gem Industry Association
• Australian Gemmologist (publication)

FAQ: Which is better, black opal or boulder opal? What is black opal? What is boulder opal? What is the difference between black opal and boulder opal? How are black opals valued? How are boulder opals valued?

Black opal has long been the most prized and most famous opal, however it’s lesser known cousin, the boulder opal, is beginning to gain recognition and popularity amongst opal lovers and the general public. So let’s compare these two types of opal and see how they stack up!

A Brief Introduction

Black opal was discovered in Australia at Lightning Ridge, New South Wales, in about the 1880’s or 1890’s and has since become famous around the world as the most brilliant and stunning opal in the world. It is highly sought after and prized around the world. Black opal is generally mined in shafts, and is usually found between 25-45 feet in ‘nobby’ (nodules of potch and colour) or ‘seam’ (horizontal deposit) formations. Black opal is considered the ‘Rolls Royce’ of opals as its dark body tone lends its colour an extra vibrancy not seen in the more common white opals found in South Australia.

Boulder opal was discovered in Australia at Quilpie, in Western Queensland, in about 1870. Since then it has risen to recognition as the second most valuable type of opal, however remains largely unknown to the general international public. Boulder opal is generally mined in open cut operations, where large amounts of dirt are cut away from the surface and removed. The ironstone boulders which contain the opal are referred to as ‘floating boulders’ due to their irregular positioning under the surface. The opal usually forms as thin veins within these boulders, and most stones are cut with the host ironstone still remaining on the back.

Body Tone

Black Opal – Black opal gets its name from its dark body tone, which ranges from dark grey to black. The darkness of the stone causes the colour to stand out much more than if the stone was white. Black opal often has a natural potch backing (colourless opal) on the back of the stone which also contributes to its dark body tone. (Note: triplets & doublets, which consist of a thin slice of opal glued to a black backing, are made to imitate black opals.)

Boulder Opal – Boulder opal also has a dark body tone (although there are some occurrences of white boulder opal), which is as dark as black opal. Because boulder opal forms in thin veins in ironstone boulders, the host ironstone is usually left on the back of the stone. This is why, if you look at the back of a boulder opal, there is a layer of brown rock attached to the back. For this reason, boulder opal is sometimes referred to as a ‘natural doublet’, as this layer of dark stone on the back gives the opal its dark body tone.

Colour & Pattern

Black Opal – Black opal may display all the brilliant colours of the rainbow, in all the patterns which opal displays, such as floral, ribbon, harlequin, straw, chinese writing, rolling flash, etc.

Boulder Opal – Boulder opal is identical to black opal in its spectrum of colours, its potential for brilliance, and in the patterns which it may display. Some argue that because boulder opal is a thin layer of opal located very close to a dark backing, it has the potential for brighter & better colour, however this is debatable.

Note: Gem quality stones (gem quality refers to extremely high quality opals) – In proportion to the amount of opal mined, there is very little difference in the quantity of rare, high quality stones which are found of each type of opal.

Stone Shape

Black Opal – The market for black opal generally demands symmetrical, oval shaped stones, with a domed cabochon, as these are the most popular shape in most jewellery.

Boulder Opal – Due to the thin nature of the opal veins which form in boulder opals, it is impossible to cut domed cabochons in most boulder opal stones. The stones are therefore usually cut into free form, irregular shapes (given the odd exception) to maximise the size of the stone and minimise the loss of opal. Boulder opals therefore often cater to a slightly different market and appeal to those who like irregular shapes in jewellery.

Strength

Black Opal – Black opal, along with white opal, is classed as having a hardness of 5.5 to 6.5 on Moh’s scale of hardness. (Diamonds being 10) Therefore it is relatively fragile stone, with a similar hardness to glass.

Boulder Opal – The opal layer in boulder opal is the same as above, however the ironstone backing which is naturally attached to the stone gives boulder opals an extra hardness and strength which gives it an advantage over other types of opal. Therefore a boulder opal will generally stand up better to impact, and be much less likely to crack than a black opal.

Rarity

Black Opal – Black opal is the rarest form of opal, and is only found in opal mining fields approximately within a 70 kilometre radius of the town of Lightning Ridge. Black opal is becoming increasingly rare and top grade black opal is not currently found anywhere else in Australia or in the world. (Unlike diamonds, which are in fact very common, black opals are genuinely rare.)

Boulder Opal – Boulder opal is currently much more readily available than black opal. The area which has the potential to yield boulder opal is much larger, and a relatively small proportion of this has been explored. The area stretches along a 200 to 300 kilometre strata in Western Queensland. Therefore, the future looks promising for boulder opal mining, as it is likely to become the only actively producing source of natural dark opal. (This is partly speculation of course).

Price

Black Opal – Because of its rarity and status, black opal carries with it a certain price attachment. Market forces determine that rare items which are highly sought-after fetch higher prices than more common items. Because of their beauty, rarity, and status, black opals fetch a much higher price in comparison to boulder opals. Some argue that black opals are overpriced, while others state simply that market forces (supply and demand) determine their value.

Boulder Opal – Boulder opals are relatively under-priced in comparison to black opals. A high quality, predominantly red black opal, which is identical to a boulder opal, may fetch prices up to seven times that of the boulder opal. Generally speaking though, boulder opals are considered to carry one third of the price of black opals, despite the fact that the cost of mining boulder opals is much more than that of black opals. Open cut mining requires much more machinery and fuel than shaft mining.

The reasons for this are as follows;

• Rarity – as stated before, boulder opals are found more commonly than black opals.
• Fame & Status – Black opals are renowned throughout the world for their rarity and beauty.
• The Ironstone Factor – Due to the natural ironstone backing and the thin nature of the opal layer, boulder opal is not traditionally priced ‘per carat’. Because ironstone is much heavier than opal, valuers consider that inclusion of the ironstone would be a distortion to a ‘per carat’ price, and therefore a lower value is applied to the stone overall. Boulder opal therefore has different valuing standards applied to it, and is sometimes valued ‘per piece’ rather than at a price per carat.  It’s important to note, however, that black opals which have a colourless black potch backing are still valued per carat, and do not receive any kind of ‘penalty’. Practically speaking, it makes little difference what is on the back of a stone once it is set into jewellery – colour and brightness are still the most important factors.

Conclusion

So there you have it. Hopefully now you’ll have an understanding of the difference between black opal and boulder opal, what makes them different, and why sometimes their value differs. It’s all part of the education process!

So which is better? The truth is – neither is better, they are both equal in quality. It all depends on the individual stone, your individual tastes, and what you value in a stone. If you value the rarity of the type of stone (the satisfaction of owning something rare), the high profile often associated with it (e.g. pink diamonds or a Rolls Royce), or an oval, dome shaped opal (as opposed to a freeshape stone), then you would probably prefer a black opal over a boulder opal. More often than not, it won’t matter what type of opal it is, once you see the one for you, you’ll fall in love with it!

• View our current stock of Australian black opals and Australian boulder opals.

If you have seen our online opal catalogue, you will have noticed a number of categories used to describe and classify each stone. This system of offering detailed information about each stone is based on the Australian Opal Ebusiness Association’s (AOEA) Opal Classification Standard, and aims to offer as much information about each stone as possible, allowing you to make an informed decision about your opal.

Clearly there is no substitute for viewing a stone in person, however we believe that our videos and pictures (in which we take meticulous care to represent our stones accurately), combined with this classification system, allows our customers to buy with confidence. Our clients are almost always pleased with their stone once it arrives, since as a general rule a stone is better in real life than in any photograph. For a good detailed run-down on how the value of an opal is determined, please see our article on valuing opals.

Our Classifications Explained:

ID – This is the unique identification number issued to each opal when it is processed.

Category – The preface Solid means that the stone is a natural cut & polished opal which does not have any kind of backing adhered to the stone to enhance the colour (as is the case with the partially fabricated stones – doublets or triplets). Queensland Boulder Opals, even though they have a natural brown ironstone backing which makes the stone darker, are still known as solid opals since this is the natural formation of the stone. Read more about the types of stones.

Black Opal refers to opal which has a dark grey to black body tone, and is generally mined in the Lightning Ridge area of New South Wales. As a general rule, black opal is the most valuable form of opal, since its dark body tone causes the colours to be more vibrant.

Boulder Opal is opal mined in Western Queensland which normally has a natural brown ironstone backing attached to the stone. Boulder opal usually has a very dark body tone and is thus generally the second most valuable form of opal.

Crystal Opal means any kind of opal which has a translucent or transparent quality (i.e. you can see through it). Translucent or transparent stones often have an enhanced clarity of colour, and for this reason it usually increases the value of a stone. The term Crystal Opal normally denotes opal with a very light body tone, however Black Crystal Opal refers to a crystal opal which has a dark body tone.

Semi-Black Opal refers to opal which has a light to medium grey body tone and is therefore not quite dark enough to be called black opal. These opals usually fall within the ‘dark opal’ category in the Body Tone Index. (See diagram further down) Semi black opal is generally found in Lightning Ridge, but is also found in White Cliffs and occasionally South Australia. This can be one of the lesser valuable forms of opal.

White Opal means opal with a white to light body tone, and is also known as milky opal. White opal is found in large quantities in South Australia, and the bulk of it does not have the same vibrancy of colour as found in other forms of opal. For this reason, it is generally one of the least valuable forms of opals. (High quality white opal is available however.)

Setting – In the case of jewelry, this indicates the carat of the gold used, and whether it is White Gold or Yellow Gold.

Weight – This refers to the carat weight of the stone. Five carats equals approximately one gram. The value of an opal is usually determined by calculate a price ‘per carat’ according to the colour and appearance of the stone, and this value is multiplied by the carat weight. When there are multiple stones, the carat weight of all stones combined is given.

Origin – The place in Australia where the stone was mined. See our article on Australia’s opal mining fields for more detailed information on each field.

Dimensions – The dimensions (width and length of the stone facing upwards) measured in millimetres. One inch equals 25.4 millimetres. In the case of a freeshape stone, the measurements are generally given at the widest points of the stone. When there are multiple stones, the dimensions of the largest stone are given.

Thickness – The measurement in millimetres of the stone’s thickness (i.e. looking at the side of the stone). This measurement is taken as close to the centre of the stone as possible. This includes any potch (colourless opal) or ironstone which is naturally attached to the back of the stone. In the case of boulder opal, the actual layer of opal can be less than 1mm thick. Our stones are cut with enough backing on them to support and stabilise the stone and give them a good shape. We never leave extra weight or thickness on the back of a stone to boost its carat weight or value.

Body Tone Index – (See Figure 1, below). This is a device used to classify the darkness of a stone. Generally a darker stone leads to more vibrancy of colour, however it depends on the individual opal. Boulder opals are always listed as having a body tone index of 0 since they cannot be classed in the same system as other opals due to their ironstone backing. Boulder opals generally have a very dark body tone however.

Transparency – Refers to the ‘diaphaneity’ (transparency) of an opal. Opaque means the stone is not transparent. Translucent means the opal has a semi-transparent nature. Transparent means you can see through the stone. This category is used to determine whether a stone has any of the properties of a crystal opal.

Shape – Refers to the shape of the stone. Freeshape means anything which is not in a standard oval shape. Cabochon refers to the dome on the top of the stone. A cabochon can effect the appearance and pattern of a stone – for example, crystal opals often look better with high cabochon, whereas black opals can look better with a low to medium cabochon. This is up to the individual stone however and relies on the skill of the opal cutter to maximise its beauty and pattern. Low Cabochon means it has a flat or hardly any dome. Medium Cabochon means it has a medium dome. High Cabochon means it has a high dome on the surface.

Colours – Lists each colour of the spectrum which is visible in the opal. Generally the most prominent colour is listed first, then the second most prominent colour and so forth. The rarity of colours is as follows – in order of the rarest (most valuable) to the most common (least valuable). Red; Orange; Yellow; Green; Blue. Red is therefore the rarest and most highly sought-after colour in an opal, and therefore fetches the highest price. Unusual colours may also occur, such as purple and aqua which can also enhance the beauty and value of a stone. Read more about how opal displays colours in our opal colour article.

Brightness – This is one of the most important ways in which we determine the value of an opal. There are three brightness ratings – Subdued, Bright, and Brilliant. These categories are quite broad and are intended to give a general indication of a stone’s brilliance. Subdued means the stone falls into this category with the least brightness – (note that it still may be a beautiful stone). Bright means the stone has a good level of brilliance and falls into the middle category. Brilliant means the stone is a real eye-catcher – has excellent brightness and falls into the top category in this classification. Brilliant is obviously the most sought-after and valuable property for a stone as it is a very desirable quality.

Pattern – This is a description of the arrangement of the colours on the face of the stone and how they appear to the eye. The most common pattern is Floral, which we use as a very broad description meaning a random and relatively indistinct pattern of opal colours. Most opals fall into this category.

More valuable patterns include Pinfire (small dots of colour sparkling like stars), Broad Flash (large sections of colour which flash brightly at certain angles), and Rolling Flash (a large section of colour in which a bright flash rolls across a section of the stone as you move it).

Even more valuable patterns include; Ribbon (Almost indescribable – Multiple rolling flashes which line up in different sections moving next to each other and in succession), Flagstone (large distinct blocks of colour), Straw (small and thin multiple lines of colour next to each other), Chinese Writing (thin strokes of colour which look like chinese writing).

The most valuable and rare pattern is Harlequin, in which blocks of colour lie next to each other and are of approximately the same size and shape (like a checkerboard). This pattern is extremely rare and is the legendary in opal circles. Many websites on the internet use the term Harlequin very liberally, so be wary of what you are buying. Traditionally a true Harlequin opal is extremely valuable and rare, and can fetch hundreds of thousands of dollars. In two decades of experience, our opal cutter has only ever seen two true Harlequin opals, just to give you an idea of their rarity.

Notes – This is where any extra description, special characteristics, faults or interesting attributes are mentioned.

Any questions? Don’t hesitate to email us!

The home of Australian Boulder Opal

Queensland produces boulder opal, an unique type of opal which is found attached to a host rock, ironstone. Boulder opal is unique to Queensland, and occurs in deposits in weathered sedimentary Cretaceous rocks in the west of the state.

Much opal mining in Queensland is carried out in ‘open cut’ mining operations, which is vastly different to shaft mining.

The Queensland opal fields are within a belt of deeply weathered Cretaceous sedimentary rocks known as the Winton Formation, which extends in a north-westerly direction from the New South Wales border at Hungerford stretching west of Cunnamulla, Quilpie, Longreach and Winton to Kynuna, a distance of about 1000 km.

Queensland’s opal mining fields are located in the west and southwest of the State, and include:

Yowah field (the southernmost field centred on the small town of Yowah—includes Black Gate)

Koroit field (north-east of Yowah)

Toompine field (east and south-east of Toompine—includes Lushingtons, Coparella, Duck Creek, Sheep Station Creek and Emu Creek)

Quilpie field (west and north north-west of Quilpie—includes some of the more productive mines in recent times—Pinkilla, Bull Creek, Harlequin, and probably the most famous of all, the Hayricks.

Kyabra-Eromanga field (west and north-west of Eromanga)

Bulgroo field (north of Quilpie field in the Cheviot Range—includes the Bulgroo, or Germans—and Budgerigar to the north )

Yaraka field—includes the mines in the Macedon Range, such as Mount Tighe

Jundah field (west of Jundah over the Thompson River—includes Jundah and Opalville mines)

Opalton-Mayneside field (centred on the old abandoned township of Opalton, and to the south in the Horse Creek – Mount Vergemont area)

Kynuna field—the most northerly field, south of the township of Kynuna.

Boulder opal is widely distributed in rocks in these areas, in generally elongated or ellipsoidal siliceous ironstone concretions or boulders ranging in size from less than a few centimetres to more than 20 cm. Concretions up to 5 cm across, known as ‘nuts’, may host a kernel of solid opal or contain a network of thin veins of opal through the ironstone. This variety of opal is prevalent at Yowah where the concretions form distinct bands—the well known ‘Yowah-nuts’.

These opal fields lie within a 300 km-wide belt of deeply weathered Cretaceous sedimentary rocks known as the Winton Formation. This extends north-north-west from Hungerford on the New South Wales border, west of the townships of Cunnamulla, Quilpie, Longreach and Winton, to Kynuna, a distance of about 1000 km.

Boulder opal is widely distributed in rocks in these areas, in generally elongated or ellipsoidal ironstone concretions or boulders, from a few centimetres, to up to 3 m across. The boulders may be confined to one or more layers or randomly distributed through the weathered sandstone. Their composition ranges from sandstone types (a rim or crust of ferruginised sandstone surrounding a sandstone core) or ironstone types (composed almost entirely of iron oxides).

The opal occurs as a filling or lining between the concentric layers or in radial or random cracks in the ironstone, or as a kernel in smaller concretions or nuts. (as found at Yowah and Koroit fields, the famous ‘Yowah-nuts’). Matrix opal is where the opal occurs as a network of veins or infilling of voids or between grains of the host rock (ferruginous sandstone or ironstone). Rare seam or band opal is also found and is typically encased in ironstone.

Pipe opal occurs in pipe-like structures which may be up to several centimetres in diameter within the sandstone and these structures may be hollow or opal-filled. Wood opal is occasionally found replacing woody tissue material.

As opposed to other sedimentary precious opal, boulder opal is attached to the ironstone, and stones are usually cut with the natural ironstone backing intact. Solid opals may be cut from the ironstone material where the opal is of sufficient thickness. Boulder opals are fashioned to standard shapes and sizes but are also cut in freeform shapes to highlight their individual beauty and to avoid wastage. Magnificent picture stones are also cut but these are mainly of interest to collectors rather than for jewellery use.

Quilpie opal fields

Looking for colour? In these parts there’s plenty of it, to be found both in the stories relating to the early settlement of the region and also that ‘colour’ which is sought from beneath the surface of the bush earth. Quilpie is best known as an opal town. It is often referred to as the home of the ‘Boulder Opal’ as the area is the largest producer of this type of opal in the world.

Located 980 kilometres west of Brisbane and 208 kilometres west of Charleville, Quilpie is the commercial and social centre of the Quilpie Shire. The name of the town was derived from the Aboriginal word ‘Quilpeta’ meaning Stone Curlew.

Relatively young, Quilpie was declared an official town on 29 April 1917, in the same year the railway line from Charleville to Quilpie was completed. Quilpie is rich in grazing history beginning with the pioneering efforts of families such as the Costello’s, Tully’s and Duracks.

Quilpie is located on the banks of the Bullo River in the famous Channel Country of western Queensland. The shire is supported through primary industries such as sheep, cattle grazing, oil, gas and opal mining. Apart from these main industries Quilpie Shire houses a keen and talented artistic community.

Winton opal fields

Rich in history, Winton was originally known as Pelican Waterhole and was first settled in 1875. The town is best known as the place that Banjo Paterson wrote Waltzing Matilda in 1895, whilst at Dagworth Station outside Winton. The first performance of the ballad was reported to be at Winton’s North Gregory Hotel on the 6th of April of the same year. Winton is recognised as the ‘home’ of Australian bush poetry, hosting the annual Bronze Swagman Award, one of the country’s most prestigious literary awards.

Queensland and Northern Territory Aerial Service (Qantas), Australia’s national airline was formed in Winton in November, 1920 and its first board meeting was held in the Winton Club on 21st February 1921.

During the Great Shearers’ Strike in the 1890s, 500 shearers camped just south of Winton and the town was placed under marshal law. This was the beginning of the foundation of the Labor Party.

Winton is famous for its water supply which thrusts its way to the earth’s surface from three artesian bores, all around 1,200 metres deep emerging at a temperature of 83 degrees celsius. The water is sourced from the Great Artesian Basin which provides water for most of Australia’s outback.

Winton is in the centre of Matilda Country, a diverse region in which vast mitchell grass plains are broken by magnificent coloured gorges, ridges and jump-ups. Visitors to the region will be amazed by the vastness of the plains and the undulating nature of the landscape. There is a wide variety of animal and bird life in the area, generally best seen around dusk and dawn on minor roads and tracks.

Day trips from Winton take visitors to Opalton, one of the oldest opal fields in Queensland; Combo Waterhole, where the swaggie of ‘Waltzing Matilda’ fame reputedly met his fate; the vintage sandstone homestead of Old Cork Station; and Lark Quarry, where 93 million year-old fossils capture a dinosaur stampede.

Opalton opal fields

The Opalton Field, also called the Fermoy Field was one of the largest and most extensively worked opal deposits in Queensland. It is a good example of typical opal country in western Queensland and offers the visitor the opportunity to experience first hand the remoteness and harsh conditions endured by the opal miners. Mining activity on the field is mostly limited to small-scale hand mining but some larger operations using heavy machinery are present in the surrounding area.

The Opalton Designated Fossicking Land was established in 1995 under the Fossicking Act 1994 by the then Department of Mines and Energy, with the co-operation of the Winton Shire Council and the landholder to provide for tourist and recreational fossicking. The Opalton Field is located about 124 km by road south-southwest of Winton. Travelling from Winton take the Jundah Road (mostly unsealed) and travel 15 km, turn left and travel a further 109 km (unsealed road) past Weona Homestead to Opalton. Visitors are requested not to call at ‘Weona’.

The Opalton area attracts large numbers of visitors and is popular with tourists as a place to “speck” or”noodle” fragments of opal or ironstone matrix from the surface or from the spoil dumps of old workings. However, known areas of shallow ground, such as the old Brilliant Claim area, may offer the more serious fossicker a chance to dig and find that outstanding gem.

Yowah opal fields

The Yowah opal field which includes the nearby area known as Black Gate is the southern-most opal mining centre of western Queensland. It is popular with tourists and fossickers as it has easy access from main roads and has shops, fuel, telephone, caravan park, and a permanent bore water supply. A small local population increases significantly during the winter season. The Yowah Fossicking Area has been established by the Department of Mines and Energy with the co-operation of the Council of the Shire of Paroo and the landholder to provide for tourist and recreational fossicking.

Yowah is about 160km west of Cunnamulla. Travelling towards Thargomindah, turn off to the right about 18km west of Eulo onto the Yowah / Toompine road and travel 48km via Alroy homestead to the Yowah-Quilpie turnoff. Continue a further 23km to Yowah; this last 23 km is unsealed. From Quilpie, drive 110km through Toompine to the Eulo / Yowah turnoff. Turn left and follow this mainly unsealed road for about 56km to the Yowah turnoff, and then continue the further 23km as above.

A feature of the Yowah field is the occurrence of precious opal in siliceous ironstone nodules generally referred to as “Yowah Nuts”. These nuts range from about 5mm to 200mm across, have a spherical or ellipsoidal shape, and show alternate concentric rings or bands of light and dark brown siliceous ironstone. There is sometimes a kernel of precious opal which is the main source of the gem. The nuts are found in layers (150 to 600mm in thickness) at depths up to 20m in a ferruginous sandstone, and are commonly associated with mudstone fragments or clay pellets. The main layer is located near the contact between the sandstone and underlying mudstone / claystone, but scattered nodules, and in some cases a second band, may occur above. The lateral continuity of the nut bands is somewhat difficult to predict owing to the irregular bedding of the strata, as well as the lack of any detailed
mapping. In some shafts, the nut band was not encountered, but the sandstone at its contact with the mudstone was found to be more ferruginous and cemented by partial opalisation into a hard band, which also contained opal in the form of seams and pipes.

The eastern part of the Fossicking Area has always been popular with tourists as a place to “speck” or “noodle” fragments of opal or ironstone matrix from the surface or shallow depth. In this area the main nut band appears to have been exposed at the surface, so that a layer of loose rubble of broken ironstone nut fragments covers the surface to a depth of about 600mm. Spotting chips of opal or fragments of matrix while digging through this
material is relatively easy with a bit of practice. Fragments may also occur on the spoil heaps of shafts from the old mining activities.

Opals from Queensland

Here’s a sample of the latest opals from Queensland currently available in our Australian opal catalogue:

Sources :

Queensland Holidays

“Opal in South Australia”, Mines & Energy Resources, SA

“Opal”, Qld Dept. of Mines & Energy

FAQ :  What is the history of opal / opals? Who discovered opals? When was opal first found?

In a cave in Kenya, Louis Leakey, the famous anthropologist, uncovered the earliest known opal artifacts. Dating back to about 4000 B.C., they most likely came from Ethiopia. Historically, opal discoveries and mining progressed similarly to the ways diamond, emerald, ruby and sapphire were produced. As early humans found various gemstones, they slowly learned to work them into decorative shapes. As communities developed, gems became symbols of wealth.

In the Old World, Hungary mined opal for Europe and the Middle East, while Mexico, Peru, and Honduras supplied their own native empires with the gemstone. Conquistadors introduced New World opal to Spain when they returned with stones in the early sixteenth century.

Since the late 1800’s, Australia has dominated opal production with more than ninety per cent of the global output. Opal of differing qualities occurs in more than twenty other countries, including Zambia, Ethiopia, Guatemala, Poland, Peru, Canada, New Zealand, Indonesia, the USA, Brazil, and Mexico.

The modern name of the gem opal is derived from ancient sources: the Sanskrit Upala – which means “precious stone”; the Latin Opalus; and the Greek Opallios which both mean”to see a color change”.

Early races credited opal with magical qualities and traditionally, opal was said to aid its wearer in seeing limitless possibilities. It was believed to clarify by amplifying and mirroring feelings, buried emotions and desires. It was also thought to lessen inhibitions and promote spontaneity. The early Greeks believed the opal bestowed powers of foresight and prophecy upon its owner, while in Arabian folklore, it is said that the stone fell from heaven in flashes of lightning. To the Romans, it was considered to be a token of hope and purity.

Ancient Romans provided the first real market for opal. With a rich powerful empire, wealthy citizens acquired disposable income and a passion for gems. Opal, whose colours changed with every shift of light, was rarer than pearls and diamonds and destined to be the stuff of myths and dreams.

Mark Antony loved opal. Indeed, it is said that he so coveted an opal owned by Roman Senator Nonius that Mark Antony banished the Senator after he refused to sell the almond sized stone, reputed to be worth 2,000,000 sesterces. (US $80,000) Mark Antony is said to have coveted the opal for his lover, Cleopatra. Legend states that one Roman Emperor offered to trade one-third of his vast kingdom for a single Opal.

Writing before his death in 79 A.D., the Roman Pliny wrote of the opal as “Having a refulgent fire of the carbuncle (ruby or garnet), the glorious purple of amethyst, the sea green of emerald, and all those colours glittering together mixed in an incredible way.”

Pliny thought the opals came from India, but the gems so eagerly sought by Rome probably came from open cut mines in Hungary, situated near Cervenica or Cernowitz (now Czechoslovakia). He had been deceived by dealers who had probably hoped to capitalise on the appeal of “oriental” imports. Hungarian opals have a milk-white background, usually with a pin-fire, small-size colour display. During the Middle Ages, more than three hundred men worked the mines in Hungary. The mines in Eastern Europe were the only source of European opal until the Spaniards returned from the New World with Aztec opal.

In the Middle Ages, the opal was known as the “eye stone” due to a belief that it was vital to good eyesight. Blonde women were known to wear necklaces of opal in order to protect their hair from losing its color. Some cultures thought the effect of the opal on sight could render the wearer invisible. Opals were set in the Crown jewels of France and Napoleon presented his Empress Josephine a magnificent red opal containing brilliant red flashes called “The Burning of Troy.”

In the late 18th and early 19th centuries, opal began to fall out of favour in Europe. It was wrongly branded as bringing ‘bad luck’, and was associated with pestilence, famine and the fall of monarchs. Queen Victoria, however, did much to reverse the unfounded bad press. Queen Victoria became a lover of opal, kept a fine personal collection, and wore opals throughout her reign. Princess Mary, Duchess of Gloucester, gave an opal ring to her niece Queen Victoria in 1849. This opal ring had been previously owned by Queen Charlotte since about 1810.

Queen Victoria’s friends and her five daughters were presented with fine opals. Opal became highly sought after because the Royal Court of Britain was regarded as the model for fashion around the world and fine quality opal had recently been discovered in far-off Australia. In the latter years of Queen Victoria’s long reign, various Australian opal fields were discovered and worked.

Discovery in Australia

The first discovery of common opals in Australia was made near Angaston (SA) by the  German geologist Johannes Menge in 1849. Both the Queensland Boulder Opal and Lightning Ridge fields attracted miners in the 1880’s. Production of precious opal began at White Cliffs (NSW) in 1890, from Opalton (Qld) in 1896, and at Lightning Ridge (NSW) in 1905.

Before 1900, rough opal was sent from White Cliffs, the premier NSW opal field, to Germany to be cut and polished. Gradually, professional cutters began appearing on the fields. They rigged up old treadle sewing machines or bicycles, designing innovative cutting/polishing gear. In 1907 at Old Town, on the Wallangulla Opal Fields (later known as the Lightning Ridge Opal Fields), the first recorded cutter was Charles Deane. When the 3-Mile broke out in 1908, cutters worked at Nettleton on 3-Mile Flat. Lorenz had learned to cut in Germany. He used horizontal wheels with a hand crank and was an expert. He made doublets, jewellery, and was one of the first to buy opal by the carat. Many miners cut their own opal, and often very roughly.

A study of the many written accounts of the time suggests that most of those early Australian discoveries were accidental – a horse’s hoof kicked up opal-bearing rock, a boundary rider’s wife discovered a pretty pebble in a creek bed, a flock of sheep was struck by lightning during a rainstorm and the run-off from the storm uncovered opal at ‘Lightning Ridge’. A number of Queensland locations also came into their own during the Depression years, when men without work were willing to chance their luck.

When Australian opals appeared on the world market in the 1890’s, the Hungarian mines spread the idea that it was not genuine, probably because gems with such brilliant fire had not been seen before. By 1932, the Eastern European mines were unable to compete with the high quality stone being produced in Australia and ceased production, allowing Australia to assume the mantle of premier opal producer of the world, becoming famous for Lightning Ridge’s colourful and rare black and crystal stone.

In South Australia, Angaston was followed by Coober Pedy in about 1912, Andamooka in about 1930, and then Mintabie. During the depression of the 1930’s the industry declined until new finds in 1946 stimulated mining and, since then, there has been a spectacular increase in production. Now over 50% of world production comes from South Australia.

A History of Opal Mining in Queensland

The history of opal in Queensland is one of heartbreak, frustration, determination and at times success at incredible odds. Rich in myths and legends, Queensland is the birthplace of the Australian Opal Industry. Opal was first discovered in Queensland on Listowel Downs, south of Blackall in 1869. The first registered mine was in 1871 south of the present town of Quilpie. Among the early miners were Berkelman and Lambert, who worked a deposit on the Barcoo in 1872-1873, and whose opal attracted great interest at the Queensland Annexe of the London International Gem Exhibition in 1873.

By 1875 there had been a number of wonderful finds and interest began to grow, but it wasn’t until, 1888 that Tullie Wollaston , a young surveyor turned entrepreneur from Adelaide made a determined effort to market the gem. In so doing he engraved his name forever across the annals of history. It was due to his sheer determination in convincing the gem merchants of the world to accept the gem that we now have a viable industry.

Opal gougers of last century were mostly shearers and station-hands who had little or no geological knowledge. George Cragg, a young stockman, discovered the northern opal fields on Warronbool Downs 100 kilometres south of Winton where the Opalton Field exists even to this day.

Two World Wars and droughts slowed the progress of Boulder Opal realising its full potential on the world stage. Although mining on a small scale continued it was relatively dormant. It was not until 1967, when Des Burton , a pharmacist from Quilpie become involved with Boulder Opal, unwittingly through his efforts, helped revitalise an industry. In the 1970’s he introduced modern opal cut mining techniques which revolutionised the opal mining industry.

Boulder Opal and the people that mine and deal with opal have supplied the industry a rich and colourful history, which has become part of Australia’s heritage. Opal has been discovered in Queensland from the Southern Borders of Western Queensland to as far north as Kynuna, this probably would be the largest opal field ever known, with opal mining centres in Winton and Quilpie.

Today the Queensland opal miner still exists, supplying the markets of the world with this most exquisite product, Queensland Boulder Opal.

Timeline – A History of Opal Mining in NSW

• 1877 – Mining for precious opal in igneous rocks begins at Rocky Bridge Creek, a tributary of the Abercrombie River, in the Central West.
• 1881 – Opal is discovered at Milparinka, near Tibooburra in the Far West.
• 1884 – Opal is discovered in sedimentary rock at White Cliffs in the Far West.
• 1889 – Precious opal is discovered at White Cliffs.
• 1880s or 1891 – Opal is discovered in sedimentary rock at Lightning Ridge (Wallangulla) and other localities in the area, but its commercial value is not recognised.
• 1890 – Precious opal mining begins at White Cliffs (continuing to 1915 then going into decline).
• 1896 – Opal is discovered at Purnanga and Grenville-Bunker Field. These occurrences are near White Cliffs and so extend the size of that opal-bearing district.
• 1897 – Opal is discovered in igneous rock at Tooraweenah, near Coonabarabran.
• 1901 – Opal is discovered in igneous rock at Tintenbar, on the Far North Coast.
• 1901-1905 – Opal mining begins at Lightning Ridge. The first shaft was put down around 1901 or 1902 by Jack Murray, a boundary rider who lived on a property nearby. Some time later, possibly a few months, a miner from Bathurst named Charlie Nettleton arrived and commenced shaft sinking. It was he who in 1903 sold the first parcel of gems from the field for $30, not a fiftieth of the price that could have been obtained five years later.
• 1908 – Opal mining begins at the Grawin-Sheepyard Field in the Lightning Ridge area, increasing the importance of the opal fields in the district.
• 1919 – Opal mining begins at Tintenbar, continuing to 1922.
• 1920 – The Newfield opal area is discovered.
• 1985 – Seminal work by the Geological Survey of New South Wales leads to better, more scientifically controlled exploration for opals.
• 1989 – The Coocoran opal area is discovered in the Lightning Ridge district.
• 1998-1999 – The estimated value of opal production in the State is about $44 million. New South Wales (and Australia) is a leading world producer of opals.

Sources :

• “Opal in South Australia”, Mines & Energy Resources, SA
• “Opal”, Qld Dept. of Mines & Energy
• Minerals NSW
• “Make your own Luck with Opal”, Jewellery World, June 2000. 
• Queensland Boulder Opal Association
• “Opals”, by Fred Ward, Gem Book Publishers, 1997.
• “Australian Precious Opal”, Andrew Cody, 1991.