If you're buying opal for the first time, understanding the different types of opal can be confusing. What is the difference between a solid opal, doublet and triplet? Is black opal always black? What makes boulder opal different? And how does Australian opal compare with Ethiopian opal?
Opals can be described according to their construction, body tone, transparency, host rock and where they were mined.
In this guide, we explain the differences between solid opal, opal doublets, opal triplets, black opal, dark opal, white opal, crystal opal, boulder opal and Ethiopian opal so you can better understand what you're buying.
What Is a Solid Opal?
A solid opal is a gemstone that consists naturally of opal throughout the stone and has not been laminated or glued to another material to enhance its appearance.
Solid Australian opals can be found in several famous opal-mining regions, including Lightning Ridge, Coober Pedy and the Queensland boulder opal fields.
Solid opal isn't a single colour or variety. A solid opal may be black, dark, white, light or crystal opal. Boulder opal is also considered solid natural opal when the naturally occurring ironstone host rock remains attached.
Because natural opals form individually, every stone has its own combination of colour, pattern, body tone, transparency and shape.
Is Solid Opal More Valuable?
Solid natural opal will generally command a higher price than an assembled doublet or triplet when comparing otherwise similar stones.
However, being solid does not automatically make an opal valuable.
An opal's value can be influenced by its brightness, play-of-colour, pattern, body tone, transparency, size, condition, origin and overall visual appeal.
A beautiful, bright opal doublet may therefore look more impressive than a lower-quality solid opal, even though their construction is different.
What Is an Opal Doublet?
An opal doublet is made from two layers.
A thin piece of precious opal is bonded to a darker backing. The darker base can enhance the appearance of the opal and make its play-of-colour appear brighter and more dramatic.
Doublets allow thin pieces of beautiful precious opal to be used when there may not be enough material to cut a traditional solid gemstone.
This makes opal doublets an attractive and often more affordable way to enjoy vibrant Australian opal.
Because a doublet contains an adhesive layer, it requires different care from most solid Australian opal. Doublet jewellery should not be soaked or exposed to water for prolonged periods, as repeated or prolonged exposure may eventually affect the bond between the layers.
What Is an Opal Triplet?
An opal triplet consists of three layers:
a dark backing;
a very thin layer of precious opal; and
a clear protective cap.
The dark backing helps enhance the opal's colour, while the clear top can protect and magnify the thin opal layer.
Triplets can display impressive colour while remaining significantly more affordable than many solid opals.
However, an opal triplet contains only a very thin layer of natural precious opal and should always be disclosed as a triplet rather than sold as a solid opal.
Like doublets, triplets should not be soaked in water or unnecessarily exposed to moisture and chemicals.
Solid Opal vs Doublet vs Triplet: What's the Difference?
The easiest way to remember the difference is by the number and type of layers.
Solid opal is naturally occurring opal without an artificially attached backing.
An opal doublet has two layers — precious opal attached to a backing.
An opal triplet has three layers — a thin slice of precious opal between a backing and a clear protective top.
All three can produce beautiful jewellery, but it is important to know which type you're purchasing because their value, construction and care requirements are different.
What Are the Different Types of Australian Opal?
Australia produces many varieties of precious opal. Some of the best-known include black opal, dark opal, white opal, crystal opal and boulder opal.
What Is Black Opal?
Black opal is one of Australia's most famous and highly prized varieties of opal and is particularly associated with Lightning Ridge, New South Wales.
Despite the name, black opal does not need to appear completely black.
The term relates to the stone's dark body tone. This darker background can create exceptional contrast, allowing the opal's play-of-colour to appear incredibly vivid.
Black opal can display flashes and patterns containing blue, green, yellow, orange, red and violet.
The combination of a dark body tone, strong brightness, desirable pattern and sought-after colours can make exceptional black opals particularly valuable.
What Is Dark Opal?
Dark opal has a body tone that is lighter than black opal but considerably darker than traditional white or light opal.
It may have a grey or dark-grey appearance that provides excellent contrast against its play-of-colour.
Dark opal can be an excellent option for people who love the dramatic appearance of darker opals.
Like all opal, its quality and value depend on much more than its classification alone.
What Is White Opal?
White opal has a light, pale or milky body appearance and is one of the most recognisable types of Australian opal.
Coober Pedy in South Australia is particularly famous for producing white and light opal.
White opal can display a complete spectrum of play-of-colour, from soft blues and greens to vibrant orange and red.
The lighter body colour often gives white opal a softer overall appearance than black or dark opal, although exceptional white opals can still display remarkably bright colour.
What Is Crystal Opal?
Crystal opal is precious opal with a transparent to semi-transparent body.
Despite its name, crystal opal isn't actually a crystal. The term describes the transparency of the opal.
Because light can enter the stone, the play-of-colour can have incredible depth and may appear to float within the opal.
Crystal opal can occur with different body tones and can display spectacular flashes of colour.
High-quality crystal opal with excellent transparency, brightness and play-of-colour can be particularly desirable.
What Is Boulder Opal?
Boulder opal is a distinctive Australian opal most famously associated with Queensland.
Boulder opal forms naturally within cracks, cavities and thin seams in ironstone boulders.
When the opal is cut, the natural ironstone is often left attached to the back of the opal.
Is Boulder Opal a Doublet?
No. This is an important distinction.
Although boulder opal may appear to have a dark backing, that backing is natural ironstone that the opal formed within.
It has not been artificially glued onto the opal.
An opal doublet, by comparison, is created by bonding a slice of opal to a separate backing material.
The contrast between colourful precious opal and natural brown ironstone gives boulder opal its distinctive appearance.
Because the cutter often follows the natural opal seams within the ironstone, boulder opals are frequently cut into beautiful freeform shapes.
What Is Ethiopian Opal?
Ethiopian opal is natural opal mined in Ethiopia and is known for producing some spectacular play-of-colour and patterns.
Ethiopian opal can display brilliant flashes of red, orange, green, blue, yellow and violet.
However, buyers should understand an important difference between much of the Ethiopian opal available today and Australian opal.
Many Ethiopian opals are hydrophane opals.
Hydrophane opal has a porous structure that can absorb water and other liquids. When it absorbs water, the appearance of the stone can temporarily change, including its transparency and the visibility of its play-of-colour.
As the stone dries naturally, its appearance may gradually return.
However, oils, perfumes, creams, soaps and other substances can also be absorbed and may affect the stone's appearance.
For this reason, Ethiopian hydrophane opal generally requires greater care around liquids, cosmetics and chemicals.
Australian Opal vs Ethiopian Opal
One of the common questions people ask when buying opal is:
Is Australian opal better than Ethiopian opal?
There isn't a simple answer because individual opals vary enormously in quality.
Both Australian and Ethiopian opal can be natural and can display spectacular play-of-colour.
However, they can have different physical characteristics.
Australian opal includes famous varieties such as Lightning Ridge black opal, Coober Pedy white opal and Queensland boulder opal.
Many Ethiopian opals on the market are hydrophane, meaning they can absorb water and other liquids. This difference is particularly important when considering how the jewellery should be cared for.
Ultimately, an opal should be assessed individually according to factors such as brightness, colour, pattern, body tone, transparency, size, condition, origin and overall beauty.
Which Type of Opal Should You Buy?
Choosing the best type of opal ultimately comes down to your personal preference, budget and how you intend to wear the stone.
If you love dramatic colour against a dark background, you may be drawn to Australian black opal or dark opal.
If you prefer a softer, classic appearance, white opal may be perfect.
For incredible depth and transparency, you may fall in love with crystal opal.
If you appreciate natural, earthy gemstones where the host rock becomes part of the finished piece, Queensland boulder opal is incredibly distinctive.
And if you're looking for beautiful opal colour at a more accessible price point, a quality opal doublet or triplet may be worth considering.
Discover Australian Opal with Cosgrove Opal
At Cosgrove Opal, we love the fact that no two opals are exactly the same.
From the dark body tones of Lightning Ridge black opal to the natural ironstone of Queensland boulder opal, every stone has its own character, pattern and story.
Understanding the different types of opal makes it easier to appreciate what you're looking at and, most importantly, understand exactly what you're purchasing.
Whether you're searching for Australian opal, black opal, crystal opal, white opal, boulder opal or a unique hand-cut opal, we're here to help you find a stone you'll treasure.