No new dated, realized per carat print landed in the colored stone market this week. We looked at Gemfields' announcements, the major auction houses and the trade press, and found nothing dated after last Tuesday that moves a row of the index. So the index holds, and we say so rather than fill the space.

A quiet week is a good time to fix a confusion we see often. Gemfields sold emeralds in May at an average our index carries at $146 per carat. In September it sold emeralds from the same mine at $9.72 per carat. Both numbers are correct. They describe different stones.

Key Takeaways

→ Nothing moved this week, and that is the data. We found no new auction result, producer sale or laboratory finding dated after October 6 that sets a per carat price for any of the 8 stones. The last Gemfields items on the trade press tracker are the September 25 profit warning and the September 11 emerald result (Mining Weekly tracker, as of October 13).

→ Kagem's September auction sold everything. The sale ran August 24 to September 10 in India. All 44 lots sold for $29.6 million at an average of $9.72 per carat. It was commercial quality rough, a different category from the higher quality sale held in May (Engineering News).

→ Commercial quality emeralds are a steady business for Gemfields. The previous commercial quality auction, in late 2025, raised $25.4 million (Mining Weekly). Revenue is comparable across the two. Prices per carat are not something we can compare from these sources, because we do not have the earlier average.

→ No date yet for the next ruby sale. Management has said it plans further auctions before year end. We found no confirmed dates, so we report none.

The index tracks the 8 reference stones every week. Each row holds until a new dated transaction moves it. No transaction landed this week, so every row holds.

Auction prices realized, not retail. Sources: Christie's, Sotheby's, Gemfields, Bonhams, GemGuide, Pala International.

Notable this week: the sapphire row is now four months old (June 9). The alexandrite row dates from December 2024. Age is a property of a row, not a signal about the stone. We would rather show an old print than invent a new one.

The numbers. May 2026, higher quality emerald auction, average $146 per carat, $26.8 million in revenue. September 2026, commercial quality emerald auction, average $9.72 per carat, $29.6 million in revenue. Same mine, Kagem in Zambia. Same seller, Gemfields (Engineering News; Gemfields).

The ratio. $146 divided by $9.72 is about 15. That is our arithmetic. It is not a price move. Nothing fell by 93 percent. Two different grades of rough were sold in two different sales.

Why the sale matters more than the mine. Gemfields sorts Kagem output into quality categories and sells each category in its own auction. A buyer in the commercial sale and a buyer in the higher quality sale are shopping for different material. A single "Zambian emerald" price per carat does not exist.

What this means for the index. The emerald row uses the higher quality May average because it is the closest to what the index tracks: stones that behave like the investment end of the market. The September average is a different product. If we averaged the two, we would publish a number nobody actually paid.

What we cannot see. The $9.72 figure is a rough average across 44 lots. It says nothing about cut stones, and rough prices do not translate directly into what a finished stone costs. We have no source for the weights in each lot, so we cannot say how many carats sold at what price inside the auction.

1. An average hides its basket. Before you compare two prices per carat, ask what quality tier each came from. A 15 times gap can be entirely composition.

2. Revenue and price answer different questions. September's revenue ($29.6 million) is higher than May's ($26.8 million), while its average price is far lower. More carats of cheaper rough can raise revenue and lower the average at the same time.

3. A quiet week is information. A market with no new prints is a market where the index should not move. If a newsletter shows a move every week, check whether a transaction stands behind it.

→ Gemfields' next ruby auction. The H1 report put a lot of weight on whether premium grade holds. A dated, realized basket is the next real test. We found no date.

→ Auction season. The autumn jewelry sales in Hong Kong and Geneva are where new dated prints for sapphire, ruby, spinel and others usually appear. We will report results, not previews.

→ Mozambique's mining law. A 15 percent state stake requirement and local processing rules were reported in June (Mining Weekly, citing Reuters). We have not seen how they apply to Montepuez, and we make no claim until we do.

Pick any auction result you have seen quoted this year. Find the quality tier or category of the lots sold, and the number of lots. If the report does not say, the average per carat is not a price you can use.

— 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: Engineering News (Gemfields' latest rough emerald auction generates $29.6m, September 11, 2026; Gemfields' latest emerald auction yields $26.8m, May 22, 2026); Mining Weekly Gemfields tracker (as of October 13, 2026); Gemfields announcements. Derived figures are marked as our arithmetic.