The $125 Million Ruby Reckoning: Why the World's Biggest Mine Is Running Short on Top-Grade Rubies

A $125 Million Signal From the Ruby Capital of the World

On September 30, 2026, Gemfields — the London-listed miner that controls the single largest source of rubies on earth — released its first-half results and delivered a jolt to the colored-stone world. The company wrote down the value of its Montepuez Ruby Mining (MRM) operation in Mozambique by $125.2 million and posted a net loss of $98.5 million, nearly four times its loss over the same period a year earlier.

The reason behind the write-down is the part every jewelry lover should notice: the mine simply isn't yielding enough high-quality rubies. Montepuez is thought to supply roughly half of the world's rubies, so when its premium production falters, it isn't just one company's accounting problem — it's a supply-side story that ripples all the way down to the stone in a finished ring.

 Photo Credit: National Jeweler.

Why the Mine Fell Short

Gemfields' interim CEO David Lovett described MRM as the company's "most significant operational and financial challenge." Two things went wrong at once. First, the deposit yielded fewer premium rubies than forecast, prompting the company to slash its life-of-mine valuation. It even revised an earlier 2025 impairment upward — from $35 million to $65 million — after finding inconsistencies in its own mine model. Second, a wetter-than-usual rainy season limited access to the best ground, forcing miners into lower-grade sections.

It wasn't all red ink. Here's how the first half actually broke down.

Encouragingly, recent recoveries have improved, and the mine's new processing plant, known as PP2, is now largely operational and at times exceeding its 400-tons-per-hour target. Lovett was careful, though, noting that a return to sustainable profitability "will require consistent execution over time rather than short-term improvements."

Translation for Ruby Buyers

Here's the simple version: the world's biggest ruby source is producing fewer top-grade stones, right as demand for fine natural rubies stays strong. When the supply of the best material tightens, the finest rubies — the vivid, untreated, well-saturated stones collectors chase — tend to hold and grow their value. We've watched this dynamic play out at auction for years, where a truly exceptional Mozambican or Burmese ruby can rival a diamond of similar size on a per-carat basis.

That doesn't mean a ruby necklace is about to double overnight. Commercial-grade rubies remain widely available, and prices move slowly. But if you've been considering a fine natural ruby — an engagement stone, an anniversary piece, or a July birthstone heirloom — news like this is a reminder that the top of the market rarely gets cheaper. Scarcity is the entire story of what makes a gemstone precious.

One Mine, Half the World's Rubies

It's hard to overstate Montepuez's role. Discovered just over a decade ago, the Mozambique deposit transformed the ruby trade almost overnight, becoming the largest and most important source on the planet — Gemfields owns a 75% stake. That concentration is a double-edged sword: it brought a flood of beautiful, well-priced rubies to market in the 2010s, but it also means a single mine's struggles can tighten global supply in a way no diamond mine could.

Meanwhile, the company's emerald operation at Kagem in Zambia delivered a healthier result, contributing $26.7 million on the back of a strong May auction. The contrast is a useful lesson for anyone buying colored stones: rubies, emeralds, and sapphires each have their own supply stories, their own origins, and their own value trajectories. There's no single "gemstone market" — there's a market for each stone.

 Photo Credit: GIA.

Frequently Asked Questions