There are many different types of opals available from all around the world. It can be difficult to know what to look for and what all the jargon means when shopping for opals. This guide aims to be your one stop for all things opal and answer your questions like “what’s the difference between Australian and Ethiopian opals?,” “Why are Ethiopian opals so cheap?,” “how do I take care of my opal jewellery?,” and “how are opals formed?” etc.


Table of contents:


Opal Care

        Opals range from 5.5 to 6.5 on the Mohs scale. Glass is 6.5 on this scale, so due care should be taken to prevent your opal jewellery from getting scratched or breaking. Opal jewellery should be removed when sleeping or doing household tasks (e.g. gardening or washing dishes) to avoid being crushed or knocked on hard surfaces. When stored it should be kept separated from other jewellery, either in the ring holder in a jewellery box or in a soft pouch to prevent harder stones or the metal of other jewellery from scratching the opals. When cleaning your opal jewellery, never allow it to be placed in an ultrasonic cleaner. The vibrations can cause the porous stones to become cracked or split apart. A mild detergent and a soft toothbrush or cloth can be used to clean any dirt or grime from the jewellery but avoid harsh chemicals and prolonged exposure to water or soap. Solid opals are fine in water, but prolonged or repeated exposure can ruin a doublet or triplet opal. Ethiopian opals should be kept dry at all times, or they can temporarily lose their colour.


How Opals are Formed

        Opals are formed from silica rich water running through the earth, settling, and filling voids within the rocks caused by natural faults or decaying fossils. The silica particles settle under gravity to form layers of silica spheres in a regular array. These silica spheres in an array diffract white light, creating the play of colour that is so prized with opals. Potch or common opal is the same hardened solution, but the silica spheres are either of too many varying sizes or too small to be noticeable. This leaves the stone colourless. Smaller silica spheres give a blue or green colour, while larger ones give red to the opal. This has caused opals with red in their play of colour to be more rare and more expensive. 

        Opal is found as two types. Most of the world’s opals are found as volcanic vesicles infill (silica rich water has filled the holes left behind in volcanic rock formed when the lava cooled) or as sandstone opals, the kind found predominately in Australia.


Types of Opals


        The most common descriptions you find with opal jewellery: solid, doublet, or triplet. Solid opals are natural opals that have had no treatments other than to cut and polish. These are the most premium form of natural opal and will have the longest life in your jewellery.

        Opal Doublets are thin slices of opal with a solid backing glued to the back, generally made of onyx or ‘potch’ (colourless/valueless pieces of opal from the mine site). These are usually black to bring out the colours of the stone and help to give some thickness and strength to the opal. It is not recommended to let opal doublets be submerged or soaked as it can ruin the glue between the backing and the opal.

Black Opal Doublet

        Opal Triplets are even thinner slices of opal, sandwiched between a backing and a clear dome of either quartz or glass. These are made to use the thin layers of opal that form in the cracks of stone. Triplets are the best value for money. They are still beautiful while utilizing the least amount of opal. As with doublets, these should not be submerged or soaked to prevent the layers from separating.


White Opal

        White opals are opals with a pale yellow to milky white body tone. These are the most common type opals found in Australia. The pale body tone doesn’t always allow for the colours to show as brightly, leading to black opals being the more sought after body tone. However, they can still be quite beautiful with stunning play of colour.


A Garrett Ray pendant featuring a solid white opal from Coober Pedy

Black Opal

        Black opals are not solid black, but have a dark body tone that ranges from black to dark blue. This dark backdrop gives the colours the most room to shine and show more clearly than white opal. Black opals tend to carry a higher price tag than their white counterparts due to the greater play of colour.


Black Opal

Crystal Opal

        Crystal opals are opals with a translucent to transparent body and can refer to either black or white opals. The transparency can lead to even greater play of colour because you can see every layer of colour within the opal, and again an even higher price tag. Especially on black crystal opals.


Crystal Opal


Boulder Opal and Matrix Opal

        Boulder opals are opals that formed in ironstone rather than sandstone and are prone to crazing during the formation. This means they form all throughout the ironstone’s cracks in networks and are often unable to be cut from the ironstone into just the opal. A boulder opal with a clean face and an ironstone backing can receive a high valuation, due to receiving the benefits of a doublet but with a completely natural formation. Many boulder opals however have a spotted face with ironstone throughout. Matrix opals are porous stones of another variety with small holes that have been filled with tiny specs of precious opal, generally sandstone. These have a makeup of more host stone than opal.


Boulder Opal


Fairy Opal

        Fairy opals are treated sandstone matrix opal. The treatments done are to darken and harden the stone. This allows it to be polished to a high shine and for the colours to sparkle more brightly on the black background. To treat the stone fairy opals preformed into shape, then they are cooked in sugar water until the sugar is carbonized, then polished.


Fairy Opal


Fossil Opal

        Fossil opals are opals that formed in cavities in the earth left behind by decaying fossils. The opals form an exact replica of what was left behind. Bones, shells, pinecones and plants. Some of our favourites are the Belemnite fossils, which were squid like cephalopods from the Jurassic period. The opals left behind are long rods and look quite magical.


Opalized Belemnite Fossil

Fire Opal

        Fire opals are opals with a deep yellow to red body tone, formed by the presence of iron oxide within the stone. The more valuable fire opals have a deeper red, a more transparent body, and richer play of colour. The transparent stones tend to be faceted rather than shaped into a cabochon (a smooth dome, how most opals are cut). The facets allow more light to refract within the stone giving it a brighter play of colour.



Synthetic Opals

        There are a few different types of imitation opals, none of which are the exact same chemical and physical properties as natural opal. According to GIA, a certified synthetic opal must:

(a) be silica in composition (major elements), possibly containing some water;

(b) be composed of submicroscopic spheres;

(c) have gemological properties with refractive index (RI) between 1.37 and 1.47

        The two main synthetic opals that have been certified by GIA are a mixture of resin and silica, between 75-80% resin and 20-25% silica. Other imitation opals are simply glass or plastic.


Synthetic Opal


Opal Regions

        Australia produces 95% of the world’s opals, but many other countries produce opals with beautiful colours. Each region’s opals have unique and interesting properties, formed by the local geology.



        Australian opals are found across South Australia, Queensland, and New South Wales, with each state producing different types of opals.

Map of Australian Opal Mines

South Australia

        South Australia has four active mine sites and produces the most opals of all the regions. They predominately produce high quality white and crystal opals with gorgeous colours.


  • Coober Pedy

        Coober Pedy is the epicentre of the world’s white opals. With one of the harshest climates in the world, locals live in caves and dugouts under the surface while also mining opals within the tunnels. The township’s name comes from the Aboriginal term ‘okupa piti’ meaning ‘white man’s burrow’.

A Coober Pedy hotel where guests can stay in a cave


  • Andamooka

        Andamooka is known for producing high quality crystal seam opals, but has largely been defunct since the 1970’s with most of the towns population working in the nearby uranium mines.


  • Mintabie

        In the 60’s and 70’s a large deposit of black crystal opal was found in Mintabie, but with a massive mining operation at it’s peak in the 70’s utilizing explosives and a fleet or large machinery the deposit was quickly stripped. Limited mining activities still occur.


  • Lambina

        One of the newest mines to begin production, Lambina began to be mined in earnest in 1996. Late 1997 miners learned of an imminent native title claim over the entire region and were able to work with the title holders made it possible to continue mining the area. The towns population sits around 300 people.



        Queensland produces predominantly boulder opal, found attached to the iron stone found in the mining fields. There are many fields currently producing opals:

  • Yowah
  • Koroit
  • Toompine
  • Quilpie
  • Kyabra-Eromanga
  • Bulgroo
  • Yaraka
  • Jundah
  • Opalton-Mayneside
  • Kynuna

        The Queensland boulder opals are found throughout the fields in rocks distributed through ironstone from a few centimetres to a few metres across, or in small nuggets. The small nuggets are referred to as ‘nuts’, and are commonly found in Yowah (hence the famous Yowah Nuts)

Yowah Nuts


New South Wales

        New South Wales has two major mine fields, producing Australia’s black opals.


  • Lightning Ridge

        Some of the most valuable opals found in the world are from the Lightning Ridge mine, producing the highest quality black opals in the world. Opals were discovered in 1880, and mining began in 1901.


  • White Cliffs

        Like Coober Pedy, White Cliffs opals are found in sandstone seams. Predominately white and crystal opals are found in the mines, but this mine is also known for its ‘opal pineapples’ which are oddly shaped opal fossils that are formed when a mineral crystal is replaced by calcite and then opal.


Opal Pineapple



        Precious opals from Ethiopia entered the market in 1994. They are commonly referred to as ‘Welo’ opal, but you may also find them called ‘Wollo’ and ‘Wello’ opals. Many of the opals found in the region have the orange to red body tone of fire opals. Black, White, and crystal opals are also found in abundance.

        Ethiopian opals are generally much cheaper than Australian opals, but this does not mean they lack in quality! Ethiopian opals are rarer than Australian opals, but there are still large quantities on the market which is currently keeping the prices down. There were major recent discoveries of deposits in 1994, 2008, and 2013. Opal sellers are also selling at lower prices currently to compete with the popularity of Australian opals.

        Ethiopian opals have a unique property where the generally translucent body tones create a beautiful play of colour, with the colours seeming to move within the opals (as opposed to flashing colours on the surface like Australian Opals). Due to the translucent bodies and large sizes Ethiopian opals are sometimes faceted like other gemstones, creating some beautiful pieces.

Faceted Ethiopian Opal

        Ethiopian opals are hydrophanes, meaning they are porous and can absorb water if submerged. This can lead to loss of colour or even cracking. They are fine to get wet as this can take a few hours of being submerged, but it is still best practice to keep Ethiopian opals dry. If they do lose their colour from absorbing water they may recover after a drying period, although this is not guaranteed.

        Some opals may be treated to enhance or change their colour. Their porosity allows them to absorb dyes and even smoke. Smoked Ethiopian opals are wrapped in paper which is burned to produce fine soot that is absorbed by the opal and darkens its body tone to produce a higher contrast.



        Opals found in Mexico are typically fire opals. They are famous for their deep orange to red body tones, ranging from cloudy to translucent. The value increases as they get bigger, more transparent, and with their level of play of colour sometimes referred to as ‘fire’ (I know, confusing.) These are some of the rarest opals in the world and command a high price.


Mexican Fire Opal

United States

        The US produces around $90,000 of opal annually (compared to Australia’s $40m average in the 1990’s and current average of ~$10m/year). They tend to be agate like in appearance or very small in size. American opal deposits are found around volcanic regions, mostly in the Midwest:

  • Louisiana
  • Arkansas
  • Utah
  • Idaho
  • Washington
  • Arizona
  • Nevada
  • Oregon


        No matter what kind of opal you prefer, they’re all beautiful! Opals may be the October birthstone, but they glitter year round. We hope this guide answered all of your opal questions, should you have any more questions feel free to contact us for more information.

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