October 04, 2026

Opaque Gemstones Are Back: Onyx, Malachite, Lapis, Coral and Turquoise

By Sasha Tarasova

Filed under Gemstone GuidesDesigner & Signed JewelryCare, Sizing & Insurance

Short answer: Opaque gemstones such as onyx, malachite, lapis lazuli, coral, turquoise, chrysoprase, carnelian and mother-of-pearl are prized for solid, saturated colour rather than sparkle. They are back because designers from Van Cleef & Arpels to Cartier built icons with them. Most are much softer than diamond or sapphire, many are routinely dyed or stabilised, and some coral is subject to trade restrictions.

For a couple of decades the fashionable stone was the one that flashed. Now the stone people ask us about is often the one that does not: a flat black onyx panel, a banded green malachite disc, a turquoise cabochon the colour of a swimming pool. Opaque stones read as graphic and modern, they sit well next to gold, and they have a long pedigree in period and signed jewelry. They also come with more treatment, more imitation and more fragility than the faceted stones most buyers are used to. Like the underrated antique gemstones we keep recommending, they give a lot of colour for the money. This guide covers both halves: the appeal and the fine print.

What counts as an opaque gemstone?

An opaque gemstone is one that light does not pass through, so its beauty comes from colour, pattern and polish rather than from light returning out of the stone. Opaque stones are almost always cut as cabochons (smooth domed tops), flat plaques, beads, carvings or inlay, never faceted for brilliance.

Many of them are not single minerals at all. Lapis lazuli is a rock, a mix of several minerals. Coral and mother-of-pearl are organic, made by living animals. Onyx, carnelian and chrysoprase are all varieties of chalcedony, a fine-grained form of quartz. That diversity is why their durability and care vary so much.

The main opaque stones, one by one

Onyx

Black onyx is a variety of chalcedony. The jet-black material in almost all jewelry, antique and modern, is dyed: naturally grey or banded chalcedony is soaked and treated so that it turns uniformly black. The practice is centuries old, the colour is stable, and the trade regards it as standard. At around 6.5 to 7 on the Mohs scale, onyx is one of the more practical opaque stones for rings.

It is also the material of the classic Art Deco black-and-white look: onyx with diamonds and platinum. That combination is so recognisable that it is heavily reproduced, and our guide to spotting a reproduction Art Deco ring covers the tells. In Victorian mourning pieces, onyx sat alongside jet, a fossilised wood, and cheaper black substitutes such as vulcanite and French jet (black glass); our guide to Victorian mourning jewelry explains how to tell them apart.

Malachite

Malachite is a copper carbonate mineral with bands of light and dark green. It was a Russian imperial obsession in the nineteenth century, and the Malachite Room of the Winter Palace in St Petersburg is the famous example. Most malachite today comes from Central Africa, particularly the Democratic Republic of the Congo.

It is soft, roughly 3.5 to 4 on the Mohs scale, and reacts with acids, including some cleaning products and cosmetics. Malachite is commonly stabilised with resin, and "reconstituted" malachite, made from crushed material bound with resin, is also on the market. Both should be disclosed.

Lapis lazuli

Lapis lazuli is a deep-blue rock composed mainly of the mineral lazurite, often flecked with gold-coloured pyrite and streaked with white calcite. The classic source is the Sar-e-Sang mines in Badakhshan, Afghanistan, which have been worked for thousands of years; Chile produces a lighter, greyer lapis.

Lapis sits around 5 to 5.5 on the Mohs scale. Lower-grade material is frequently dyed to deepen the blue and sometimes waxed or resin-treated. Imitations include dyed jasper and dyed howlite, and manufactured lapis-like products exist. Top lapis is an even, intense violet-blue with fine, scattered pyrite and little or no white.

Coral

Precious coral is the skeleton of marine animals, chiefly species of the genus Corallium, made of calcium carbonate. Mediterranean red coral, carved for centuries at Torre del Greco near Naples, is the classic source for antique and Victorian coral jewelry. Colours run from pale pink ("angel skin") to deep red ("oxblood").

Coral is soft (about 3 to 4) and sensitive to acids, heat and chemicals. It is often dyed, and cheaper materials such as dyed bamboo coral are sold as red coral. It also raises a legal question, covered below.

Turquoise

Turquoise is a hydrated copper aluminium phosphate, historically sourced from Iran (the Nishapur mines produced the classic "Persian blue") and from the American Southwest. It is around 5 to 6 on the Mohs scale and porous, which means it absorbs oils and can change colour over years of wear, often shifting towards green.

Turquoise is one of the most treated gems on the market. A large share is stabilised, impregnated with resin to harden it and fix the colour. Some is dyed. "Reconstituted" turquoise is compressed powder bound with resin. And dyed howlite and magnesite are common imitations. Untreated, natural turquoise of good colour is a specialist item and priced as one.

Chrysoprase

Chrysoprase is an apple-green chalcedony coloured by nickel, with Queensland in Australia the principal modern source. At roughly 6.5 to 7 it is reasonably durable. Its colour is generally natural, although dyed green chalcedony is sold as a cheaper substitute, and some chrysoprase can pale with prolonged heat or strong sunlight.

Carnelian

Carnelian is orange to red-brown chalcedony. It is one of the oldest carved gems, used for seals and intaglios since antiquity, which is why it appears so often in antique signet rings. Much carnelian on the market has been heated to deepen or even out the colour, and some is dyed agate. It is hard enough, around 6.5 to 7, to wear daily in a ring.

Mother-of-pearl

Mother-of-pearl is nacre, the iridescent lining of mollusc shells, the same material that forms the outer layers of pearls. It is soft (around 3.5), sensitive to acids, perfume and dehydration, and prone to chipping at thin edges. Our guide to natural and cultured pearls covers nacre in more detail. Mother-of-pearl in jewelry is usually cut as thin plaques, which is why it is so often backed or set in a gold frame.

Opaque gemstones compared

Hardness decides how a stone survives daily contact. Our Mohs hardness guide explains the practical cut-off: anything much below 7 will gradually scratch from ordinary dust, which contains quartz.

Why are designers so attached to opaque stones?

Because opaque stones behave like colour on a painter's palette. They can be cut into precise flat shapes, fitted edge to edge, and set flush with metal. That makes them ideal for graphic designs that faceted stones cannot achieve.

Van Cleef & Arpels Alhambra

The Alhambra line, introduced in 1968, is built on a four-leaf clover motif framed in gold with a beaded edge. Its most recognisable versions use opaque materials: mother-of-pearl, onyx, malachite, carnelian, turquoise, lapis lazuli and chrysoprase, among others. The design's success rests on that flat, even colour inside a precise gold outline. It is also one of the most counterfeited designs in jewelry. Our guide to how to tell if a Van Cleef Alhambra is real covers the details.

Cartier in the Art Deco years

Cartier's 1920s and 1930s work paired black onyx, coral, jade and lapis with diamonds and platinum, in strict geometric compositions and Chinese- and Egyptian-inspired designs. The spotted panther motif was also first rendered with onyx and diamonds. These pieces set the template for the black-white-red palette that still reads as Art Deco.

David Webb and the American hardstone look

New York jeweler David Webb, best known for enamel animal bracelets in the 1960s, also used coral, lapis, carved rock crystal and other hardstones in bold, sculptural gold settings. His work is one reason big, chunky opaque colour is associated with American glamour of that period.

We are an independent dealer, not affiliated with or authorised by Van Cleef & Arpels, Cartier, David Webb or any other house mentioned here. Final authentication of any signed piece rests with the house itself or a qualified specialist, and no checklist replaces handling the piece. Our signed and designer jewelry is described on that basis, and you can find more in the Journal's designer jewelry section.

Dyed, stabilised, reconstituted: what do the words mean?

Opaque stones are treated more often than not, and the vocabulary matters because it drives price.

• Dyed. Colour has been added. Standard and stable for black onyx; a meaningful value reduction for lapis, turquoise and coral.
• Stabilised. A porous stone, usually turquoise or malachite, has been impregnated with resin to harden it and fix the colour. Common and acceptable when disclosed, but priced well below natural material.
• Reconstituted. Powder or fragments bound with resin into a block, then cut. It is still made of the named material, but it is not a natural stone in any meaningful sense and is priced accordingly.
• Imitation or simulant. A different material made to look like the named stone, such as dyed howlite sold as turquoise, or plastic sold as coral.
• Composite or backed. A thin slice of stone or shell glued to a backing, common with mother-of-pearl and turquoise.

The FTC Guides for the Jewelry Industry (16 CFR Part 23) expect sellers to disclose treatments that significantly affect value. Our fuller guide to gemstone treatments covers where the line sits for each stone.

Is coral legal to buy?

Usually yes for antique coral jewelry, but it depends on the species, the country and the circumstances. Some coral species are subject to international trade controls under CITES, the Convention on International Trade in Endangered Species. Black coral, for example, is covered, and some precious coral species have been subject to listings or proposals over the years. Rules differ between countries and between import, export and domestic sale.

For a buyer, the practical points are these. Buying antique coral jewelry within one country is generally uncomplicated. Shipping coral across borders can require documentation. And if you are travelling or buying from abroad, check the current rules before you commit, rather than relying on a seller's assurance. We would rather lose a sale than send a piece that gets seized at customs.

How do you care for opaque gemstones?

Gently, and with fewer chemicals than you use on diamonds. Most opaque stones are softer, more porous or more chemically reactive than faceted stones.

1. Never put them in an ultrasonic or steam cleaner. Vibration and heat can crack, craze or strip treatments from porous and organic stones.
2. Clean with a soft, damp cloth. For hard chalcedonies (onyx, carnelian, chrysoprase), a little mild soap in lukewarm water is fine. For coral, pearl, malachite and turquoise, a damp cloth only, then dry immediately.
3. Put jewelry on last. Perfume, hairspray, sunscreen and lotion are the main enemies of turquoise, coral, malachite and mother-of-pearl.
4. Keep them away from acids, including household cleaners, vinegar and some cosmetics.
5. Store separately in soft pouches, so diamonds and harder stones cannot scratch them.
6. Avoid prolonged heat and strong sunlight, which can fade chrysoprase and dry out organics.
7. Have settings checked on inlaid and bezel-set pieces. A lifted edge on a flat inlay tends to chip.

How to buy an opaque-stone piece without regret

1. Ask what the stone is and whether it is treated, in those words, and get the answer on the invoice.
2. Look at the colour for evenness. Perfectly even, saturated colour in lapis, turquoise or coral can indicate dye. Dye sometimes concentrates in cracks or drill holes.
3. Check edges and corners for chips. On inlay and Alhambra-style pieces, look where stone meets metal.
4. On signed pieces, judge the gold work first. Weight, finish, hallmarks and construction are harder to fake than the stone.
5. For coral, ask about species and cross-border rules before you buy from abroad.
6. Buy for wear, not for trend. A malachite ring worn every day will scratch. Earrings, pendants and necklaces suit soft stones better. And fashion cycles are not a value strategy; our honest view of jewelry as an investment applies to opaque stones as much as to diamonds.

Questions people actually ask

Is black onyx a real gemstone?

Yes. Black onyx is a natural variety of chalcedony, a fine-grained quartz. Almost all black onyx used in jewelry has been dyed to achieve its even black colour, a practice centuries old that the trade regards as standard and stable. Glass and plastic imitations exist, but dyed chalcedony is the real material the market calls onyx.

Can you wear a malachite ring every day?

You can, but it will show wear. Malachite is soft, around 3.5 to 4 on the Mohs scale, and reacts with acids found in some cleaners and cosmetics. A daily ring will gradually lose polish and pick up scratches. Malachite suits earrings, pendants and occasional rings better, or a design with a protective raised metal frame.

How can you tell if turquoise is real?

Not reliably by eye. Dyed howlite and magnesite often show dye collecting in dark veins and cracks, and plastic feels warm and light. Distinguishing natural, stabilised and reconstituted turquoise usually needs a gemmological laboratory. For any piece sold as natural untreated turquoise at a premium, ask for written confirmation of treatment status.

Is antique coral jewelry legal to own and sell?

Owning antique coral jewelry is generally legal, and domestic sale is usually straightforward. Some coral species, such as black coral, are subject to CITES international trade controls, and moving coral across borders can require documentation. Rules vary by species and country, so check current regulations before buying from abroad or travelling with it.

What stones are used in Van Cleef & Arpels Alhambra?

The Alhambra collection is best known for opaque materials set in a beaded gold frame, including mother-of-pearl, onyx, malachite, carnelian, turquoise, lapis lazuli and chrysoprase, along with other stones and diamond-set versions. The mix of materials has changed over the decades. ZHIVA is not affiliated with Van Cleef & Arpels, and authentication rests with the house or a qualified specialist.

Why is my turquoise turning green?

Natural turquoise is porous, and over years it absorbs skin oils, lotions and cleaning products, which can shift the colour towards green. Stabilised turquoise resists this better. The change is usually permanent, so prevention is the only cure: put turquoise on after cosmetics, wipe it after wearing, and keep it away from water and chemicals.

Looking for a specific opaque-stone piece, a period onyx and diamond ring, a Victorian coral set or a signed hardstone design? Our sourcing service runs that search, and more coloured-stone guides are collected under gemstones in the Journal.