The Weekly Carat Index
Five market signals on colored stones, in five minutes.
Colored stones don't have an earnings season. Just private, opaque, stone-by-stone pricing. That's why this newsletter exists.
Gemfields' first-half 2026 numbers just landed — the closest thing to a quarterly report the sector gets.
Headline: auction revenue up 72%, to $102.9 million. Reality: revenue rebounded. Grade did not.
Key Takeaways
Auction revenue: $102.9M, up ~72% YoY. Net debt down to $44.2M.
Premium ruby recovery at Montepuez: still weak, 0.025 ct/tonne.
The Carat Index holds. October's ruby auction is the number that moves it.
THE 5-MINUTE MARKET
→ The rebound is real. $102.9M H1 revenue, up ~72% from $60M. Net debt down to $44.2M from $61.2M. (Rapaport; National Jeweler; Diamond World)
→ The number that matters is buried. Premium ruby recovery at Montepuez: 0.025 ct/tonne, still weak. The fine-ruby squeeze flagged in July — now confirmed over six months. (Gemfields; Rapaport)
→ Emerald steady. Kagem held healthy output despite rising costs. PP2, the second ruby plant, nearing full commissioning. (National Jeweler; TipRanks)
THE CARAT INDEX — HOLDS
The index tracks 8 reference stones, weekly. Each row holds until a new dated transaction moves it.
A revenue update isn't a per-carat print. The index holds — this report just confirms the ruby supply story.
Stone | Reference | $/carat | Δ |
|---|---|---|---|
Sapphire | Kashmir 15.49 ct, Christie's NY, Jun 9 2026 | $138,700 | ▲ vs Apr ($130,400) |
Ruby | Mozambique mixed-quality avg, Gemfields Feb 2026 | $279 | ▼ vs Jun 2025 ($461) |
Emerald | Zambia avg, Gemfields May 2026 | $146 | ▼ vs Sep 2025 ($161) |
Alexandrite | Brazil 16.53 ct, Sotheby's NY Dec 2024 | $115,000 | → |
Tourmaline (Paraiba) | Brazil 13.54 ct Tiffany, Christie's NY | $310,000 | → origin science under review |
Spinel (Mahenge) | 18.17 ct red, Bonhams May 2022 | $35,000 | → |
Garnet (tsavorite) | fine 2+ ct, trade benchmark (high) | $8,000 | → |
Tanzanite | AAA 5+ ct, single source, Merelani | $1,200 | → |
Auction prices realized, not retail. Sources: Christie's, Sotheby's, Gemfields, Bonhams, GemGuide, Pala International.
Notable this week:
Ruby and emerald — two of eight rows — are anchored on Gemfields auctions.
H1 numbers don't move either row. But they raise confidence behind both.
Next figure that moves ruby: October's Mixed-Quality auction.
FOCUS OF THE WEEK
Why it matters. Gemfields is the dominant traceable producer of both emerald and ruby. Two of the eight index rows are effectively priced off its sales — this report is the closest thing the category gets to an earnings call.
The 72%, decoded.
H1 2025 was a low point: emerald ops suspended into oversupply, ruby auctions thin.
The rebound ran on volume and format, not premium prices. June's ruby auction: $23.1M at just $66.30/carat.
Real recovery, not a re-rating.
Metric | H1 2025 | H1 2026 |
|---|---|---|
Auction revenue | $60.0M | $102.9M (+72%) |
Net debt | $61.2M | $44.2M |
MRM premium ruby grade | — | 0.025 ct/tonne |
Emerald output (Kagem) | suspended into oversupply | healthy, costs rising |
Gemfields unaudited operational update, 30 July 2026. Audited results due 25 September.
The grade is the tell. Premium ruby recovery: 0.025 ct/tonne. A mine working harder for less. Revenue can be managed. Grade cannot be talked up.
The overhang. Gemfields flagged: declining grades, PP2 still unfinished, security disruption at Montepuez, delayed VAT refunds. September 25's audited numbers will show how much of the $102.9M reaches the bottom line.
THREE THINGS THAT MATTER
1. Read the base before you cheer. Up 72% is a recovery from a crisis low — not a re-rating. Only genuine price gains justify paying up for fine material.
2. 0.025 ct/tonne is the real signal. A full half-year confirms the structural squeeze in fine Mozambican ruby. Over 2–3 years, that supports top-tier prices even as headline averages stay soft.
3. Two dates govern the ruby row. September 25: audited results. October: the next Mixed-Quality auction — the number that actually moves the index.
WHAT WE'RE WATCHING
→ September 25 — audited results. EBITDA and cash flow will show if the recovery is profitable, or just busy.
→ PP2 commissioning. Clean landing: volume rises into 2027. Slip: the grade problem bites harder.
→ October's ruby auction. The next comparable per-carat read against February's $279.
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ONE THING TO DO BEFORE NEXT TUESDAY
Next time you read a triumphant producer headline, do two things before you believe the boom:
Find the base it's measured against.
Find the grade coming out of the ground.
Revenue is a story management can shape. Grade per tonne is the number the earth writes.
— Carat Brief
Carat Brief is editorial. Nothing here is investment, legal, or tax advice. Gemstones are illiquid and require certified verification before purchase. Work with credentialed labs: GIA, AGL, SSEF, Gübelin, Lotus Gemology.
Sources: Gemfields Group operational update, 30 July 2026; Rapaport; National Jeweler; Diamond World; IDEX; TipRanks. Auction averages vary by lot composition and are not directly comparable across formats.