Rome Resources Plc (AIM:RMR), the explorer focused on critical minerals in the Democratic Republic of Congo, has raised the estimated tin content of its Kalayi deposit by 45%.
The upgrade places the deposit among a small group of high-grade tin resources, at a time of rising prices for the metal.
Kalayi, part of the Bisie North project in the eastern DRC, now holds an inferred resource of 0.46 million tonnes grading 1.47% tin, containing about 6,760 tonnes of the metal.
A mineral resource estimate is a geologist's assessment of how much metal a deposit contains and at what concentration, known as grade.
The new figure marks a 45% rise in contained tin against the maiden estimate published in October 2025, alongside a 32% increase in tonnage and a 10% improvement in grade.
Expanding a resource usually lowers its average grade, but at Kalayi both the quantity and the grade rose, the latter from 1.33% to 1.47% tin.
The company said this was unusual and reflected greater confidence in the geology, drawn from wider ore intervals in its 2026 drilling.
Rome also identified ground immediately to the south-east, along the same high-grade trend, that it believes could double the size of the resource with further drilling.
The company cautioned that exploration might not intersect additional tin. Its geological model now maps 11 separate mineralised zones, up from seven a year ago, with two further zones not yet counted in the estimate.
Kalayi is one of two advanced targets at Bisie North. The second, Mont Agoma, is a separate polymetallic system holding a maiden resource of 3.16 million tonnes grading 1.45% copper, with additional zinc, tin and silver.
Copper is trading at or near record levels, which the company said added to that deposit's appeal.
Tin is changing hands at about $50,000 per tonne, well above the $36,600 assumed in the October 2025 estimate.
The market is marked by a structural supply shortfall, with few new high-grade deposits under development and existing mines facing falling grades.
Paul Barrett, chief executive, said resource growth without grade dilution "reflects improving geological confidence".
Rome said it was continuing talks with potential strategic partners over developing Bisie North, where pilot mining is advancing towards a full licence.
The company is targeting a combined 20,000 tonnes of contained tin across the project.
The estimate was prepared by The MSA Group, an independent mining consultancy, under Canadian reporting standards.
