Six weeks ago, this newsletter looked past Gemfields' headline 72 percent revenue jump and pointed at a smaller, buried number instead: premium ruby recovery at Montepuez, stuck at 0.025 carats per tonne. The conclusion then was that revenue can be managed with format and volume, but grade cannot be talked up, and grade was quietly saying the fine end of the ruby market was getting scarcer.

Gemfields has now put a number on exactly that problem, and it is a large one. On September 25, the company warned it expects a net loss of $73.5 million for the first half of 2026, driven by a $125.2 million non-cash impairment against the Montepuez ruby mine. The grade story did not go away between August and now. It got quantified.

Key Takeaways

→ Gemfields warned of a $73.5 million H1 loss, against $20.5 million a year earlier. The swing is driven almost entirely by a $125.2 million non-cash impairment charge against Montepuez, reflecting a more conservative forecast for future premium ruby recovery. The company also revised its 2025 impairment upward, from $35 million to $65 million, after identifying a further $30 million adjustment (IDEX Online; Rapaport; Mining.com).

→ Revenue still rose, but management itself flagged the comparison as distorted. Total auction revenue reached $102.8 million, up from $60 million, with Montepuez contributing $76.1 million and Kagem $26.7 million. Gemfields said the year on year jump is skewed by the deferral of a mixed quality ruby auction from December 2025 into February 2026, which pushed a full auction's worth of revenue out of one comparison period and into the other (Solitaire; Jewellery Focus).

→ Full audited results land tomorrow. Gemfields will publish its complete interim financial statements and hold a management webcast on September 30, one day after this edition. EBITDA, free cash flow, and a detailed explanation of the impairment are expected then. This week's numbers are the warning. Next week's edition covers what the full report actually says.

The index tracks the 8 reference stones every week. Each row holds until a new dated transaction moves it. An impairment charge is an accounting event, not a per carat auction print, so it does not move the ruby row on its own. It does, however, harden the case behind where that row already sits.

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

Notable this week: an impairment does not set a per carat price, but it is the clearest possible confirmation of a supply thesis. Gemfields, the entity that actually mines the rock, is telling its own shareholders it now expects less future value from Montepuez than it thought even a year ago. That is a company, not a newsletter, saying the premium ruby squeeze is real and getting worse, in a legal filing rather than a market comment.

What an impairment actually is. A non-cash impairment is not a loss of money that already left the building. It is management and auditors formally lowering their estimate of how much future value an asset will produce, and writing that lower number into the accounts today. No cash moved on September 25. What moved was Gemfields' own official belief about Montepuez's future, and it moved down by $125.2 million in one half, on top of an already restated $65 million impairment for 2025. Companies do not take a charge like this lightly. It is the accounting system forcing a hard admission that a forecast was too optimistic.

Why this is more informative than the revenue line. Revenue can be shaped by format, timing, and which lots go into which auction, exactly the distortion Gemfields itself pointed to when it flagged the deferred December auction. An impairment is comparatively hard to spin. It requires the company to formally justify, to auditors, why it now expects less from an asset than it previously told the market to expect. When a 0.025 carat per tonne premium recovery rate, flagged here in August as the real signal, ends up translating into a nine figure write down five weeks later, that is the grade story converting from a mining statistic into a balance sheet fact.

The revision to 2025 is the more uncomfortable detail. Gemfields did not only take a fresh charge against 2026. It went back and added $30 million to last year's impairment, taking it from $35 million to $65 million. That is the company saying its own prior estimate, made only months ago, was itself too generous. A single downward revision can be a one off. A second, larger revision to a number already revised once suggests the ground at Montepuez has been surprising the company's own geologists repeatedly, in the same direction, for over a year.

What still needs the full report to answer. A profit warning gives the headline loss and its main cause. It does not give EBITDA, free cash flow, or management's granular explanation of the extra $30 million swing on 2025. Those numbers, due September 30, will show whether the underlying cash generating business is stable beneath the write down, or whether the impairment is one symptom among several. Gemfields itself says recent ruby recoveries show early signs of improvement. Tomorrow's report is the first chance to see whether that improvement shows up anywhere in the actual cash numbers, not just in a sentence in a press release.

1. An impairment is a company's own admission, and that makes it high quality evidence. Nothing else in this market lets a producer's own auditors force a documented, numbered correction to a previous forecast. When it points the same direction as the operational data already in hand, weight it accordingly.

2. Be as skeptical of a flattering comparison as of an unflattering one. Gemfields flagged its own revenue growth as partly a timing artifact from a deferred auction. That is good disclosure. Apply the same scrutiny to any other producer's year on year percentage before treating it as a clean read on demand.

3. Tomorrow's numbers matter more than this week's headline. A profit warning is management controlling the narrative around bad news before the full disclosure lands. The audited report on September 30 is where the real detail, EBITDA, free cash flow, and the explanation for the restated 2025 figure, actually surfaces. Read that report before drawing conclusions from this one.

→ September 30, audited interim results and webcast. One day away. EBITDA, free cash flow, and management's own explanation of the impairment and its 2025 revision. Full coverage next Tuesday.

→ October's Gemfields Mixed Quality ruby auction. Still the next like for like per carat read on the ruby row, and now also the first real test of whether the "early signs of improvement" in recoveries actually show up in a saleable basket.

→ November, Christie's Hong Kong and Geneva. The larger autumn test continues regardless of Gemfields' results, and remains the venue to watch for the top of the index.

Next time a producer reports a headline revenue gain, look for the sentence where the company itself explains what the number does not mean, a timing shift, a deferred sale, a distorted comparison. That sentence is usually more honest than the headline it sits next to. This week, the more important sentence was not about revenue at all. It was the one about a mine being worth $125 million less than the company thought it was six months ago.

— 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: IDEX Online; Rapaport; Mining.com; Miningmx; RTT News; Solitaire (GJEPC); Jewellery Focus. Figures are drawn from Gemfields' September 25, 2026 trading update; audited interim results are due September 30, 2026.