Most people assume diamonds sit at the top of the rarity scale. They don't. With roughly 130 million carats mined globally each year, diamonds are among the more abundant gemstones on the market. Their reputation has more to do with decades of marketing than genuine geological scarcity.
We handle thousands of gemstones every year at our showroom in The Rocks, Sydney — and we've seen firsthand how collectors react when they learn that some of the stones in our cases are far rarer than any diamond they've encountered. Black opals from Lightning Ridge, certified Argyle pink diamonds, and a handful of other extraordinary stones make diamonds look almost commonplace by comparison.
Here are 12 gemstones that are genuinely rarer than diamonds, ranked by geological scarcity, market availability, and collector demand.
1. Black Opal
Black opal is not just the rarest type of opal — it's one of the rarest gemstones on Earth. Over 95% of the global supply comes from a single source: Lightning Ridge in New South Wales, Australia.
What sets black opal apart is its dark body tone, which creates the perfect backdrop for intense flashes of colour known as play-of-colour. When a black opal displays red fire against a dark base — particularly in a harlequin pattern — you're looking at a stone that can command $10,000 to $20,000 per carat or more at current market values.
Other opal varieties exist — white opal, crystal opal, and boulder opal — but black opal remains the most valuable by a significant margin. The gap between a good black opal and a great one is enormous, and it comes down to brightness, pattern, and the range of colours visible in the stone.
In our experience working with over 4,000 opals across 15 years, the single most common mistake buyers make is judging an opal from a photograph. Play-of-colour is a three-dimensional phenomenon — it shifts as the stone moves in your hand, and no image captures that properly. That's why serious opal buyers visit in person.
What to look for: A dark body tone (N1–N4 on the body tone scale), broad flash patterns, red as the dominant play colour, and brightness that fills the face of the stone rather than appearing in isolated patches.
Browse our Australian opal collection →
2. Argyle Pink Diamonds
Fewer than 0.01% of all diamonds mined globally show any pink colour. Of those, the vast majority came from one source: the Argyle Mine in Western Australia's remote Kimberley region. That mine closed permanently in November 2020, and no comparable deposit has been found since.
During its 37-year operation, pink diamonds represented less than 0.1% of Argyle's total output. At peak production, the mine yielded over 90 million carats of rough diamond per year — and only a tiny fraction showed any pink hue. The stones that made it through grading to "Fancy Vivid Pink" are, quite simply, among the rarest objects human beings have ever collected.
Argyle pink diamonds get their colour not from trace elements (the way yellow diamonds get theirs from nitrogen, or blue from boron) but from structural distortions deep within the crystal lattice — plastic deformation caused by extreme geological pressure over billions of years. That mechanism is unique and has never been replicated at scale by any other mine.
Since the mine's closure, prices for certified Argyle pinks have risen sharply. A Fancy Vivid Pink can reach hundreds of thousands of dollars per carat. Even Fancy Light Pink stones from Argyle now carry significant premiums because of verified provenance and finite supply.
We hold certified Argyle pieces in our pink diamond collection and can walk you through grading, certification, and the differences between Fancy Light, Fancy Intense, and Fancy Vivid classifications. This is a purchase where provenance documentation matters enormously — and where seeing the stone under controlled lighting makes all the difference.
What to look for: Argyle certification, GIA grading report, pure pink hue (without brown or orange modifiers), and intensity grade of at least Fancy Intense for investment-quality stones.
Explore our pink diamond collection →
3. Painite
For decades, painite held the Guinness World Record as the rarest mineral on Earth. Discovered in Myanmar in the 1950s by British gemologist Arthur C.D. Pain, only two crystals were known to exist until the early 2000s. More specimens have surfaced since, but gem-quality painite remains extraordinarily scarce.
It's a borate mineral with a striking orange-red to brownish-red colour, caused by trace amounts of chromium and vanadium. Painite also displays pleochroism — it shows different colours depending on the viewing angle. Museum-grade specimens can reach $60,000 per carat, though most collectors will never encounter one outside a dedicated mineral show.
4. Taaffeite
Taaffeite has one of the most unusual origin stories in gemology. Austrian-Irish gemologist Count Edward Charles Richard Taaffe identified it in 1945 — not by finding it in a mine, but by spotting it among a batch of cut spinels he'd purchased from a Sri Lankan dealer. It was the first mineral ever identified from a faceted gemstone rather than a rough crystal.
With a soft lavender to mauve colour, taaffeite is often mistaken for spinel even today. Only a handful of faceted stones exist in private collections. It's found primarily in Sri Lanka and Tanzania, and new discoveries remain exceedingly rare.
5. Red Beryl (Bixbite)
Red beryl is estimated to be roughly 1,000 times rarer than diamond. It's found in only one commercially viable location on Earth: the Wah Wah Mountains of Utah, USA.
While it belongs to the same mineral family as emerald (both are beryllium aluminium silicates), red beryl gets its deep red colour from manganese rather than chromium. Most crystals are too small or too fractured to cut, and gem-quality specimens over one carat are virtually non-existent. That single-source origin means supply is fixed — once existing deposits are exhausted, there may never be more.
6. Alexandrite
Alexandrite is the gemstone that performs a magic trick in plain sight. Under daylight, it appears green to blue-green. Under incandescent light, it shifts to red or purplish-red. This colour-change phenomenon — caused by the way chromium interacts with different light wavelengths — is more dramatic in alexandrite than in any other gemstone.
Discovered in Russia's Ural Mountains in 1830 and named after Czar Alexander II, high-quality natural alexandrite with strong colour change is genuinely rare. Most material on the market today comes from Brazil, Sri Lanka, and East Africa, but stones with the vivid green-to-red shift seen in original Russian specimens are almost impossible to source.
7. Musgravite
First discovered in 1967 in Australia's Musgrave Ranges (South Australia), musgravite is so rare that only a handful of faceted gems surface each decade. Additional occurrences have been confirmed in Greenland, Madagascar, and Tanzania, but gem-quality material remains scarce enough that most gemologists will never see one in person.
Musgravite is closely related to taaffeite — so closely that distinguishing between them requires advanced testing. Prices for faceted specimens can exceed $30,000 per carat, driven entirely by scarcity rather than mainstream market demand.
8. Paraíba Tourmaline
When copper-bearing tourmaline was discovered in the Brazilian state of Paraíba in the 1980s, its electric neon blue-green colour was unlike anything the gem world had seen. The reaction was immediate — prices surged and have never come back down.
Similar geological conditions later produced copper-bearing tourmaline in Mozambique and Nigeria, but supply across all sources remains extremely limited. Fine Paraíba tourmaline can reach $80,000 per carat or more. For every 10,000 diamonds mined, roughly one or two Paraíba tourmalines emerge from the Earth.
9. Red Diamonds
Red is the rarest natural diamond colour. Fewer than 30 true red diamonds are known to exist, and most weigh under half a carat. Unlike pink diamonds (which derive their colour from structural distortion), the mechanism behind pure red colour in diamonds is still debated among gemologists.
The Moussaieff Red Diamond (5.11 carats) and the Hancock Red (0.95 carats) are among the most famous examples. When red diamonds do surface at auction, they consistently set per-carat price records. They remain the only diamond colour for which no reliable synthetic process has been commercialised.
10. Benitoite
California's state gemstone, benitoite is found almost exclusively near the San Benito River in San Benito County. It's a brilliant blue stone with strong dispersion (the ability to break white light into spectral colours), giving it a fire that can rival diamond under the right conditions.
Benitoite also fluoresces a vivid blue under UV light, making it a favourite among mineral collectors. Deposits are extremely limited, and most gem-quality stones weigh less than one carat.
11. Tanzanite
Found in only one location on Earth — the Mererani Hills near Mount Kilimanjaro in Tanzania — tanzanite was discovered in 1967 and brought to global attention by Tiffany & Co. shortly after. Its vivid blue-purple colour is produced through heat treatment of brownish zoisite crystals, and the result can rival fine sapphire at a fraction of the cost.
However, tanzanite's single-source origin is a double-edged sword. Geologists have estimated that the known deposits could be depleted within 20 to 30 years at current mining rates, which would make existing stones significantly more valuable over time.
12. Imperial Topaz
Imperial topaz — the rich golden-orange to pinkish-orange variety — is far rarer and more valuable than the common blue topaz most people encounter in high-street jewellery. The finest specimens come from Brazil's Ouro Preto region, where they've been mined since the 18th century.
What makes imperial topaz distinctive is its natural colour. Most topaz on the market is colourless or pale, then irradiated and heat-treated to produce blue. Imperial topaz achieves its warm hues naturally, and untreated stones with strong saturation are genuinely scarce.
What Actually Determines Gemstone Rarity?
It's worth stepping back from the individual stones to understand what "rare" actually means in gemology. Rarity isn't a single measurement — it's the intersection of several factors.
Geological formation conditions. Some gemstones only form under extremely specific combinations of pressure, temperature, and chemical composition. Black opal requires silica-rich groundwater to seep through ancient sandstone over millions of years — conditions that exist in meaningful quantities only at Lightning Ridge. Argyle pink diamonds required tectonic forces that deformed their crystal structure at depths exceeding 150 kilometres — conditions so unusual that a single mine produced over 90% of global supply.
Number of known sources. Red beryl has one viable mine. Tanzanite has one geographic source. Benitoite has one county. When a gemstone's entire global supply depends on a single location, any disruption — mine closure, regulatory change, depletion — can make it permanently unavailable. This is exactly what happened with Argyle pink diamonds in 2020.
Gem-quality yield. Mining millions of tonnes of rock doesn't guarantee gem-quality material. For every 10,000 white diamonds recovered, only one pink diamond is suitable for fine jewellery. Most painite crystals are too small or too included to cut. The ratio of rough material to cuttable gems determines how many stones actually reach the market.
Market availability vs. geological occurrence. A mineral can be geologically rare but irrelevant to the jewellery market if it's too soft, too small, or too dull to use in a setting. The gemstones on this list are rare AND desirable — a combination that drives both collector interest and long-term value.
Are Rare Gemstones a Good Investment?
We get asked this question regularly at our showroom, particularly about black opals and Argyle pink diamonds. The honest answer is nuanced.
Gemstones that have both genuine scarcity and strong collector demand — like certified Argyle pinks and fine Lightning Ridge black opals — have historically appreciated in value. Since the Argyle mine closed in 2020, prices for certified stones have risen substantially. Black opal prices from Lightning Ridge have followed a similar trajectory as new supply tightens.
However, gemstones aren't liquid assets. Unlike shares or gold, there's no exchange where you can sell a gemstone at an established market price with a click. Selling requires finding the right buyer, and that process takes time and expertise.
Our recommendation: buy gemstones primarily because you want to own and enjoy them. If they also appreciate in value — as quality black opals and Argyle pinks have consistently done — that's a welcome benefit, not the core reason for the purchase.
Can Synthetic Gemstones Match the Value of Natural Rare Gems?
Lab-grown diamonds, including lab-grown pink diamonds, are now widely available. They're chemically identical to natural stones and significantly less expensive. But they don't carry investment value, and they don't replicate the geological story that makes natural stones collectable.
A natural Argyle pink diamond formed over a billion years under conditions that no longer exist and came from a mine that will never reopen. A lab-grown pink diamond was created in a reactor last month. Both are beautiful — but one is finite, and the other is not. That distinction drives the price gap, and it will only widen as natural supply continues to shrink.
If you're weighing up the two, our article on lab-grown vs natural diamonds goes deeper into the comparison.
How to Verify the Authenticity of a Rare Gemstone
Authentication matters more with rare gemstones than with any other jewellery purchase. Here's what we recommend based on 15 years of sourcing and verifying gems:
Certification from a recognised laboratory. For diamonds, GIA (Gemological Institute of America) is the global standard. For coloured gemstones, look for reports from GIA, Gübelin, SSEF, or the Australian Gemological Association. Argyle pink diamonds should carry the mine's own certification alongside a GIA report.
Provenance documentation. Where was the stone mined? How did it reach the market? For high-value stones like Argyle pinks, a documented chain of custody from mine to retailer significantly increases both confidence and resale value.
Buy from specialists, not generalists. A jeweller who handles thousands of opals has the experience to distinguish a $500 stone from a $5,000 stone — and to identify synthetic or treated material that a generalist might miss. That expertise protects you in a way that price alone cannot.
See These Rare Gemstones in Person
Photographs don't do justice to any of the gemstones on this list — but that's especially true for opals and coloured diamonds, where colour play and light interaction define the entire experience.
Our showroom in The Rocks, Sydney houses one of Australia's largest collections of Australian opals and certified Argyle pink diamonds, with over 4,000 pieces available to view. Our team can walk you through everything from opal body tones and types to pink diamond grading — no appointment necessary, though we recommend one for high-value viewings.
In Sydney? Visit our showroom at C8/200 Cumberland Street, The Rocks — get directions.
Interstate or regional Australia? Browse our collections online or send us an enquiry and our team will respond within 24 hours. We serve customers across every Australian capital and ship nationally with full insurance.