'Opal' is one word for four rather different gems. Body tone — the darkness of the canvas behind the play-of-colour — sorts the family, drives the price, and decides the drama. The field guide, from the country that produces almost all of them.
Black opal: the pinnacle
A dark body makes colour detonate — reds and blues burning against near-black. Effectively a one-town phenomenon (Lightning Ridge), and the rarest of all: fine black opal trades per-carat with important sapphires. The full story is in our black opal guide.
Boulder opal: colour in the stone's own frame
Queensland opal cut with its ironstone host as a natural dark backing — black-opal drama at friendlier prices, in shapes the rough dictates. No two remotely alike; collectors love them for exactly that.
Crystal opal: the window
Translucent to transparent body with colour floating inside — hold it to light and the stone becomes an aquarium of fire. Underrated and, we would argue, the connoisseur's sleeper pick.
White opal: the classic
The pale, milky standard-bearer from Coober Pedy — gentle pastel fire, honest prices, and most people's first opal love.
The one test that matters: solid
Doublets and triplets — thin opal slices glued to backings — imitate black opal at a fraction of the price. Legitimate when disclosed, a swindle when not: check the side profile for layer lines, and beware 'black opal' bargains. Our buyer's guide covers the full inspection, and care guide the aftercare.
Every opal in our collection is natural solid Australian stone, assessed in-house — the way the national gem deserves.
Continue your gem education
How to Buy Opals · Black Opal · Australia's Opal Fields · browse all Gem Guides — or explore Australian opals.
What else decides an opal's value, once body tone is settled
Body tone does the most work, but it is not the whole grade. Two stones of the same tone can sit a long way apart on brightness, the colours present, pattern, how much of the face fires, cut, size and freedom from cracks and sand — which is why a bright white opal will outrank a dull dark one. Each driver is taken in turn, in the order the trade weighs them, in what determines an Australian opal's value.
This is also why opal is sold by the piece as often as by the carat. Weight is a poor guide when face size and shape do most of the talking, and that is most obvious in Boulder Opal, where the rough dictates the outline and no two stones are remotely alike.
None of these need to be at maximum for a stone to be worth wearing. A bright white opal with a clean face and a considered cut is an honest gem, and much of the Australian Opal Under $500 range sits exactly there.
Explore the Australian Opal Collection — including boulder opal, opal earrings, and gift pieces under $250.
Common questions
What are the four main types of Australian opal?
Black opal, boulder opal, crystal opal and white opal. Black opal has a dark body tone and comes principally from Lightning Ridge in New South Wales. Boulder opal is Queensland opal that formed in seams and pockets through ironstone, cut with the host ironstone left on the back. Crystal opal is transparent to translucent with the play-of-colour floating inside the body, and white opal is the pale, milky type from Coober Pedy and the South Australian fields. You can see how the types differ across the <a href="/collections/australian-opal-collection">Australian Opal Collection</a>.
What is body tone, and why does it decide so much?
Body tone is the darkness of the material sitting behind the play-of-colour, running from near-black through to milky white. A darker body gives the colours something to burn against, which is why black opal reads so strongly and why boulder opal, backed by its own ironstone, gets some of the same effect. Darker tone is generally rarer, so body tone is both the thing that sorts the family and the first thing a grader looks at.
How do I tell a solid opal from a doublet or a triplet?
Look at the stone from the side rather than the face. A doublet is a slice of opal bonded to a dark backing and a triplet adds a clear cap over that, so the edge shows straight, flat join lines where a solid stone shows one continuous piece. Doublets and triplets are not fakes and they are perfectly legitimate when disclosed, but they are worth less and they are more vulnerable to water and long immersion, so an unusually cheap "black opal" deserves a careful look. Every stone we sell is assessed in-house by an FGAA-qualified gemmologist, certification is available on request, and our terms are set out in <a href="/pages/our-guarantee">Our Guarantee</a>.
Is opal hard enough for a ring worn every day?
Opal sits about 5.5 to 6.5 on the Mohs scale — softer than sapphire at 9 and softer than quartz at 7 — so everyday grit can scratch it. It has no cleavage, but it does not tolerate a hard knock or a sudden change in temperature. Worn daily, an opal is better in a setting that shelters the stone, such as a bezel or protective shoulders, which is the first thing we discuss when you <a href="/pages/design-your-ring">Design Your Ring</a>. <a href="/collections/australian-opal-earrings">Australian Opal Earrings</a> and pendants ask far less of the stone.
How should opal be cleaned?
Warm soapy water and a soft cloth, nothing more. Never put opal in an ultrasonic or a steam cleaner: opal is hydrated silica that holds water — commonly a few per cent, sometimes up to around twenty — and it is sensitive to sudden temperature change. Doublets and triplets need more care again, because the bonded layers do not like water or long immersion, so they should never be soaked.
Sources and further reading
- Opal Description — GIA Gem Encyclopedia — Gemological Institute of America
- Opal Quality Factors — GIA — Gemological Institute of America
These are independent gemmological authorities, cited so our statements can be checked against them. Ministry of Gems® is not affiliated with these organisations. Checked August 2026.