Why Mine Closures Are Driving Rare Gemstone Prices Higher

In the time it takes a collector to commission a bespoke piece, another major mine has gone dark. Diavik closed in March 2026 after 23 years. De Beers suspended Venetia, South Africa’s highest-value operation, for two years from mid-2026. Koidu, Sierra Leone’s largest producer, halted in May 2025.

Read individually, these look like unrelated corporate decisions taken in a soft market. Read together, they trace a single structural pattern: the supply floor beneath the world’s rarest stones is dropping, and it is not being rebuilt.

This is not a story about one gem or one auction. Colored gemstone imports into the United States rose 136% between 2020 and 2024, even as origin sources closed or ran down. That collision between accelerating demand and permanently shrinking supply is the engine driving rare gemstone prices higher across multiple categories at once.

Here is what the supply data actually tells you about where value is concentrating, and why the window for acting on it may be narrowing.

The supply floor is gone: a decade of closures that will not reverse

Start with the raw diamond numbers, because they set the scale. According to Kimberley Process data, worldwide rough diamond output fell from roughly 176.7 million carats in 2005 to 98.8 million carats in 2025. That 2025 figure alone represented an 8-8.4% volume decline from the 107.9 million carats produced in 2024, and it carried a value of approximately $9.23 billion, averaging $93.43 per carat.

The Kimberley Process production statistics, which aggregate standardised rough diamond output and trade data across participating nations, confirm the sustained multi-decade volume decline that individual mine closures have only accelerated.

Now walk the closures forward, because volume decline is an abstraction until you attach it to specific mines.

Ellendale closed in 2015, removing a significant source of yellow diamonds. Argyle ceased operations in November 2020, taking with it roughly 90% of global pink diamond supply. Diavik produced its final carats in March 2026 after yielding more than 150 million carats over 23 years, with decommissioning now stretching to 2029. Venetia went into a two-year suspension in mid-2026. Ekati halted open-pit mining at Point Lake in 2025, laying off hundreds. Finsch in South Africa and Kao in Lesotho both suspended in mid-2026. And Koidu in Sierra Leone stopped in May 2025, shedding more than 1,000 workers.

Here is why the distinction matters. In an ordinary commodity cycle, production restarts when prices recover. Most of these sources cannot restart, because they are either geologically exhausted or politically frozen. That makes the supply floor effectively permanent, and it is the context without which every price figure below would mislead you.

The distinction between a temporary production halt and a permanent geological exhaustion is central to how markets reprice supply risk; mine closure economics show that restoration timelines, decommissioning costs, and jurisdictional uncertainty conspire to make restarts far rarer than the commodity cycle playbook suggests.

Colored gemstone origins: depletion without replacement

The colored stone side has followed the same track, quietly. The Batalha mines in Brazil, the primary origin for Paraíba tourmaline, shut in 2016 after a government crackdown on illegal extraction. Kashmir has seen no new sapphire production since the early twentieth century. Burmese ruby and sapphire exports remain persistently restricted, high-quality Mahenge spinel deposits are seeing rapid productivity declines, and Tanzanian tanzanite is estimated to have only about a decade of productive life left.

The critical difference from diamonds is replacement. Lab-grown diamonds exist as a substitute at scale. No synthetic credibly reproduces the optical signature and provenance premium of these origin-specific stones at the fine-gem tier, which means depletion here has no technological backstop.

How lab-grown diamonds redirected billions toward colored stones

The colored gemstone surge did not arrive out of nowhere. It began with a deflationary shock in the natural diamond market.

Lab-grown diamond technology has compressed natural diamond prices at the commercial level, with reported declines of 18-23% in recent years (a figure that remains unverified and should be treated as directional rather than confirmed). For jewellers and dealers, that compression attacked margins directly, and the response was to reposition inventory toward natural colored gems that carry provenance, certification, and optical properties no synthetic can replicate at scale.

Lab-grown diamond market dynamics have restructured the commercial price stack in ways that extend well beyond the jewellery counter, compressing natural diamond valuations at the mid-market tier and redirecting significant institutional capital toward origin-certified colored stones that no synthetic process can credibly replicate.

Follow the money as it migrated, and the demand surge looks less like independent enthusiasm and more like a direct consequence of the diamond market’s disruption. The migration split by price tier:

• High-end buyers moved toward Paraíba tourmaline, unheated sapphires, and fine spinel, chasing scarcity and provenance.
• Mid-market buyers rotated into garnet, standard spinel, and unusual sapphire varieties, pushed by higher gold costs and a desire for differentiation at accessible price points.
• Natural pearl demand broadened as collectors reached beyond traditional cream tones.

The industry has even changed its vocabulary to accommodate the shift.

Fine jewellery specialist Joanna Hardy notes that the trade is increasingly reclassifying any durable, visually appealing, and sufficiently scarce stone as “precious” rather than “semi-precious.”

That reclassification matters more than it sounds. It effectively expands the investable universe beyond the traditional big three of ruby, sapphire, and emerald, across the roughly 50 gemstone varieties currently used in global jewellery.

The 136% import surge tells you this is not a niche collector fashion. It is a market-level realignment, and it has already begun compounding against the supply constraints from the previous section.

Natural pearls: scarcity without a mine closure to blame

Pearls illustrate the same demand pressure through a different supply mechanism. There is no mine to close. Instead, environmental degradation has reduced natural mussel populations, tightening availability at the source.

As scarcity has deepened, collector interest has broadened past traditional cream-coloured specimens toward pink, silver, and lavender tones. Hamilton & Inches chief executive Victoria Houghton has pointed to this growing scarcity narrative as a driver of that widening interest.

What the auction records actually prove about scarcity pricing

The clearest evidence sits in the auction results, and the pattern worth noticing first is breadth. Records are falling across multiple distinct stone categories inside the same 24-month window, which is what separates a market-wide repricing from isolated enthusiasm for a single gem.

Paraíba tourmaline is the cleanest supply-to-price case. With Batalha closed since 2016, top-quality stones appreciated over 45% in 2025 alone, prices have nearly doubled across three years, and top-tier Brazilian material now exceeds $300,000 per carat. At Christie’s New York in December 2025, a Brazilian Paraíba achieved over $311,000 per carat.

Unheated sapphires provide the second proof point. GRS-certified Ceylon stones of 2-5 carats posted 13-15% year-on-year appreciation in 2026, while fine unheated Ceylon blue sapphires have gained 25-45% since 2020. The premium multiple for unheated over equivalent heated stones widened from roughly 2.5x at the start of 2025 to 3.2-3.5x by August 2026.

Spinel and alexandrite show the pattern runs cross-category. Spinel valuations rose around 15% annually over the preceding decade, but exceptional Mahenge neon stones have appreciated 50-80% in recent years and more than 150% since the pandemic. At Sotheby’s Geneva in May 2024, a 16.53-carat Brazilian alexandrite set a world record at $1.9 million, roughly $116,000 per carat.

*Entries marked unverified have not been independently confirmed and should be treated as indicative.

The single most dramatic verified benchmark came from Hong Kong.

At Christie’s Hong Kong in November 2025, the “Royal Blue” necklace, featuring 16 Kashmir sapphires totalling 104.61 carats, sold for more than $16.1 million, breaking the world auction record for a Kashmir sapphire necklace.

Auction records function as price discovery anchors for the wider market. When records fall across Paraíba, Kashmir sapphire, alexandrite, and spinel in a compressed window, it signals that institutional buyers, not just individual collectors, have priced in the structural supply story.

Exceptional diamond discovery pricing at the top of the quality distribution reinforces rather than contradicts the supply-floor argument: when a single stone of extraordinary scale and colour reaches the market against a backdrop of declining aggregate output, the price response reflects both intrinsic rarity and the scarcity premium buyers now attach to any verified high-quality natural material.

The risks that qualified analysts will not let you skip

The structural case is strong. It is not, however, frictionless, and treating auction records as a proxy for your own accessible returns would be a mistake. Four risks deserve full weight:

• Liquidity: these are alternative assets with long selling periods.
• Authentication and origin: pricing depends entirely on provenance and treatment status.
• Lab-grown competition: synthetics threaten the commercial tier.
• Valuation complexity: subjectivity raises overpayment risk.

Liquidity is the most structurally underestimated of the four. Average selling periods run to 6-8 months against 2-3 days for financial assets (both figures unverified but directionally consistent with alternative-asset behaviour), and liquidation for stones above $100,000 can stretch to 3-6 months.

Investment-grade stones are generally recommended as five-to-seven-year minimum holdings.

Authentication risk is equally fundamental, because investment-grade pricing is tied strictly to provenance, treatment, and origin. Buying without independent certification from bodies such as GIA, IGI, or GRS carries real valuation risk, since seller-issued certificates can misrepresent origin, mask treatments, or pass synthetics off as natural.

The lab-grown threat is real but tiered. Synthetic sapphire and ruby pose a deflationary risk to the $500-$3,000 per carat commercial segment, mirroring what lab-grown diamonds did to commercial natural stones. The structural case is strongest for material that cannot be credibly replicated and weakest for commercial-grade goods.

Valuation complexity underpins all of it. Grading turns on market fashion, optical minutiae, and stone-specific rarity, which means the thesis is only investable in practice for buyers who already hold both specialist access and patient capital.

What the supply data tells you about where pricing pressure concentrates next

Pull the threads together and the asymmetry is clear. The closures are permanent or multi-year, demand has structurally realigned toward colored stones, and price discovery is confirming the thesis across several categories at once. Industry voices at Sotheby’s, Phillips, the AGTA, and The Sapphire Bank all describe the value gap between fine unheated stones from premier origins and commercial material as structural rather than cyclical, which is the strongest signal that the repricing has further to run.

The forward-looking distinction that matters most is between scarcity already priced and depletion not yet fully reflected:

• Already priced: fine Brazilian Paraíba tourmaline above $300,000 per carat, and record-setting Kashmir sapphire.
• Depletion documented, pricing lag remaining: tanzanite, with roughly a decade of productive life left, and Mozambique Paraíba tourmaline rising around 10% annually.

The sharpest asymmetry sits in that second group, where the depletion timeline itself sets a limit on how long the lag can persist.

Tsavorite investment fundamentals follow the same origin-scarcity logic driving Paraiba and Kashmir sapphire valuations, with East African deposit depletion and the absence of any credible synthetic substitute concentrating pricing power in certified fine material from documented sources.

Given liquidity and authentication constraints, the investable entry point is not “rare gemstones” as a category. It is specific stones with independent certification, documented origin from a closing or depleted source, and a five-to-seven-year hold you can actually commit to.

This article is for informational purposes only and should not be considered financial advice. Investors should conduct their own research and consult with financial professionals before making investment decisions.

Past performance does not guarantee future results, and price projections remain subject to market conditions and various risk factors. Several figures cited above are unverified and should be treated as directional rather than confirmed.