Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Opal Buying Guide: Types, Colors & How to Choose
Opal Buying Guide: Types, Colors & How to Choose
To choose an opal, start with its play-of-color: how bright the flashes are, how much of the stone they cover and which colors show up. Then check the body tone (light, gray or black), whether the opal is natural, lab-created or assembled, and whether it has been treated. Opal rates 5 to 6.5 on the Mohs scale, so it is safest in earrings and pendants, or in a ring with a protective setting.
That is the short answer. The longer one walks through the main types of opal, what pushes the price up, how to read a listing and how to look after the stone once it is yours. Opal shares October with tourmaline, and our October birthstone guide puts the two side by side.
Opal at a glance
| Property | Opal |
|---|---|
| Material | Hydrated silica with no crystal structure |
| Body colors | White, gray, black, colorless, yellow, orange and red |
| Mohs hardness | 5 to 6.5 |
| Birth month | October, shared with tourmaline |
| Anniversary | Traditional gem for the 14th wedding anniversary |
| Natural or lab-created | Both are sold; glass and plastic imitations also exist |
| Common treatments | Impregnation with oil, wax or polymer; sugar-acid and smoke treatments to darken the body color |
| Ultrasonic or steam cleaner | No |
| Everyday wear | Earrings and pendants; rings with care and a protective setting |
| Usual cut | Cabochon (a smooth dome); some freeform and carved shapes |
What makes opal different
Most gemstones are crystals. Opal is not. It is silica, the same compound as quartz, but without an orderly crystal lattice, and it holds a little water inside its structure. That water is part of why opal needs gentler handling than sapphire or topaz. Strong heat, very dry air or a sudden temperature change can leave it with a network of fine cracks, which the trade calls crazing.
The flashes are called play-of-color. Inside precious opal, tiny silica spheres are stacked in a regular grid, and the gaps between them split white light into spectral colors. Sphere size decides which colors you get. Small spheres give blue and violet. Larger ones reach orange and red. Common opal has spheres that are uneven or jumbled, so it shows no flashes at all, only a flat, often milky color.
Types of opal
Jewelers sort opal two ways: by its background color, called body tone, and by where and how it formed. These are the names you will see most in listings.
| Type | What it looks like | Known source | Note for buyers |
|---|---|---|---|
| White (light) opal | Pale, milky body with color flashes | Australia, including Coober Pedy | The opal most people picture |
| Black opal | Dark gray to black body tone that makes the flashes look stronger | Lightning Ridge, New South Wales, Australia | Usually the most valued type |
| Crystal opal | Transparent to semi-transparent, with play-of-color | Australia and other sources | Can have a light or dark tone |
| Boulder opal | Thin seams of opal in brown ironstone, cut with the rock left on the back | Queensland, Australia | Natural backing; often freeform shapes |
| Fire opal | Transparent yellow, orange or red body, with or without play-of-color | Mexico | Often faceted instead of cut as a dome |
| Ethiopian opal | Mostly white to colorless body, often with bright flashes | Wollo area, Ethiopia | Many are hydrophane and soak up water |
Australia supplies most of the world's precious opal, which is why so many type names come from Australian fields. Ethiopian opal needs one extra warning. Hydrophane stones absorb liquid, so one that soaks up water can turn clear and lose its flashes until it dries, and oils or lotions can stain it. Keep Ethiopian opal out of the sink and away from hand lotion.
Natural, lab-created, imitation and assembled opal
Origin affects an opal's price more than almost anything else, so confirm it first.
Natural opal formed in the ground. Our natural opal pieces say so on the listing, and several also say the stone is not enhanced.
Lab-created opal is grown in a laboratory. It has opal's silica makeup and real play-of-color, usually in a more regular pattern than a mined stone, and it costs less. The lab-created opals in our listings are noted as impregnated, which means a stabilizing material fills tiny pores in the stone.
Imitation or simulated opal is another material, usually glass or plastic, made to look like opal. Opalite, for instance, is a glass. None of these are opal.
Doublets and triplets are assembled. A doublet is a thin slice of natural opal glued to a dark backing such as ironstone, black glass or common opal, which makes the colors look deeper. A triplet adds a clear cap of quartz, glass or plastic on top to protect that slice. The top layer is real opal, but an assembled stone is worth less than a solid one with the same look, and soaking can weaken the glue. A seller should always tell you when an opal is assembled.
The round pendant is 925 sterling silver with rhodium plating and holds a single natural opal. It measures 12.4 mm wide and 10.2 mm long, 16 mm overall. The 14K yellow gold necklace is smaller and simpler: a heart outline with one round natural opal of 0.08 carats at its center, on a polished rope chain with a spring ring clasp. More gold and silver options are in our birthstone necklaces.
From the Birthstone Company collection
Lab-created opal in sterling silver
All three are 925 sterling silver with rhodium plating. The round pendant measures 17.5 mm long, and the heart is a petite 6.5 mm wide and 9.1 mm long. The XO bracelet runs lab-created opal along 7.5 inches of polished links, 6 mm wide, and fastens with a box catch. Every listing notes the opal is impregnated, so none of them goes in an ultrasonic cleaner.
How to judge opal quality
Opal has no grading system like the diamond 4Cs. Jewelers still look at the same few things, roughly in this order.
Play-of-color
Brightness comes first. Some opals flash from across a room, while others need tilting under a lamp before you see anything. Next is coverage: flashes across the whole face beat a few patches. Then the color range. Red is the least common flash color, so an opal showing red and orange along with green and blue usually costs more than one showing blue and green alone.
Pattern
Pinfire is a scatter of small, tight points of color. Flash patterns are larger patches that appear and vanish as the stone moves. Harlequin is a mosaic of broad, angular patches, and it is rare and highly prized. Apart from harlequin, pattern is mostly down to taste.
Body tone and transparency
A darker body makes the same flashes look more saturated, which is why black opal sits at the top of the market. Light opals look softer, and they sit easily next to white metals and pale clothes. Transparency is a separate question. A crystal opal shows color from inside the stone, not only on its surface.
Cut, size and condition
Most opals are cut as cabochons, because a smooth dome shows play-of-color well. Small jewelry stones are usually described in millimeters, such as the 4 mm and 5 mm studs further down, while larger loose stones are sold by carat weight. Before buying, look over the surface in good light for crazing. A crazed opal is worth much less and is more likely to break.
| Factor | What to look for |
|---|---|
| Brightness | Flashes you can see without tilting the stone |
| Coverage | Color across the whole face, not in one corner |
| Color range | Red and orange flashes are rarer than blue and green |
| Pattern | Pinfire, flash or harlequin; harlequin is the rarest |
| Body tone | Darker tones make colors look stronger |
| Condition | No crazing or visible cracks |
| Disclosure | Natural, lab-created, imitation, doublet or triplet, plus any treatment |
Opal colors, explained
When people talk about an opal's color they can mean two different things: the body color behind the flashes, or the flashes themselves. A white opal usually shows pastel blue, green and pink flashes on a milky body. A black opal shows the same spectral colors against a dark ground, so they look sharper. Fire opal is named for its orange to red body, and some fire opals have no flashes at all. Lab-created opal comes in many body colors, and blue is a popular one in sterling silver jewelry.
The blue ring is sterling silver with rhodium plating and a round lab-created blue opal in a bezel, in sizes 6, 7 and 8; its listing notes the opal is impregnated. The other is 14/20 gold filled, meaning a thick layer of 14K gold bonded over a base metal core. It sets a round white opal, which the listing calls a Bello opal, in a bezel on a 1 mm band, in sizes 5 through 9. A bezel wraps the stone's edge in metal, which suits a soft stone worn on the hand. Our stackable rings have more stones to pair them with.
Which jewelry suits opal
Opal's 5 to 6.5 is below the 7 of the quartz grains in household dust, so a ring worn every day slowly loses its polish. That is why we steer opal toward earrings and pendants first. Those pieces rarely hit anything.
| Jewelry type | How opal wears | What we suggest |
|---|---|---|
| Earrings | Low exposure to knocks | A great place for opal, any setting |
| Pendants and necklaces | Low exposure | A great place for opal, any setting |
| Rings | High exposure: hands touch everything | Bezel or protected setting; take off for chores and the gym |
| Bracelets | Medium to high exposure | Bezel setting, worn now and then |
The setting matters too. A bezel runs a rim of metal around the stone and shields its edge. Prongs let in more light and show more of the opal, but they leave the edge exposed, so check them about once a year.
The white gold pair is 14K white gold with rhodium plating, set with 4 mm natural opal cabochons on posts with push backs. The yellow gold studs hold a 5 mm natural opal each. The leverbacks are 14K yellow gold too, with 4 mm round natural opal cabochons, 13 mm long overall, and a hinged lever that closes against the ear. Their listing says the opals are not enhanced. Our birthstone earrings cover the other eleven months.
If you want an opal ring, pick one you can take off for washing up, workouts and gardening. Prong-set opals look bright, but they ask for a little more care.
This ring sets a natural oval opal in prongs between two small round diamonds, on a 2 mm band of 14K yellow gold, in size 7. The listing says the opal is not enhanced. Our guide on how to choose a birthstone ring compares settings in more detail.
Reading an opal listing
Before you buy, check that the listing answers these questions:
- Is the opal natural, lab-created or an imitation?
- Is it a solid stone, or a doublet or triplet?
- Has it been treated? Look for words like impregnated, smoke treated or sugar treated.
- How big is the stone, in millimeters or carats?
- What metal is it set in, and is the setting a bezel or prongs?
Budget follows those answers. Lab-created opal is the low-cost way to get strong color. In our own range, lab-created opal pieces in sterling silver start under $35, while the natural opal earrings in 14K gold above run from $146.42 to $210.89. Black and boulder opal sit at the top of the market.
Opal as a gift
Opal is the October birthstone and the traditional gem for a 14th wedding anniversary, so it covers two gift dates. A locket gives it a place to hold a photo too.
The locket is 14K yellow gold with a polished finish and a natural heart-cut opal on the front, and it opens to hold a photo. It measures 19 mm wide and 18.8 mm long, 25 mm overall. For more ideas, see our birthstone jewelry gift guide, the birthstone Christmas gift guide, or the full October birthstone collection.
How to care for opal
- Clean solid opal with lukewarm water, a drop of mild soap and a soft cloth, then dry it right away. Wipe doublets and triplets with a damp cloth instead of soaking them.
- Never use an ultrasonic or steam cleaner on opal.
- Keep it away from strong heat and sudden temperature changes, like hot dishwater.
- Put opal on after perfume, hairspray and lotion.
- Store it in its own soft pouch, since harder gems and metal clasps will scratch it.
- Have a jeweler check ring prongs and bezels about once a year.
Our jewelry basics guide covers metal care as well.
Opal buying questions
Is opal a good choice for an engagement ring?
It can be, with care. At 5 to 6.5 on the Mohs scale, opal scratches and chips more easily than sapphire or diamond. Choose a bezel or a setting that protects the edge, and take the ring off for chores and exercise.
What is the most valuable type of opal?
Black opal, mostly from Lightning Ridge in Australia, is usually the most valued, because its dark body makes the flashes look strongest. Bright red flashes and a harlequin pattern push value higher in any type.
How can I tell if an opal is a doublet or triplet?
Look at the stone from the side. A doublet shows a straight join line with a dark layer below, and a triplet also has a clear dome on top. Many are set in closed-back settings that hide this, so ask the seller directly.
Is lab-created opal real opal?
It shares opal's silica makeup and shows real play-of-color, but it was grown in a laboratory, not mined. Imitations such as opalite glass are a different material and are not opal.
Can opal get wet?
A quick rinse is fine for solid opal. Do not soak it. Doublets, triplets and hydrophane Ethiopian opal are the most sensitive, so keep them out of water.
Can opal go in an ultrasonic cleaner?
No. The vibration and heat can crack opal or damage fillers in treated and lab-created stones. Use lukewarm soapy water and a soft cloth.
Why does opal crack?
Strong heat, a sudden temperature change or a hard knock can crack it, and some opals develop crazing, a web of fine cracks, as they dry out.
Related guides
Not sure which month's stone to buy? Our month-by-month birthstone finder has all twelve. For the stones on either side of October, read the November birthstone guide and the December birthstone guide.
Found the type of opal you like? Browse our opal jewelry in natural and lab-created stones, set in sterling silver and gold.
