Mining giant Anglo American has written down the value of its troubled De Beers diamond business by another 2.3 billion US dollars (£1.7 billion) amid a slump in demand for the precious gems.

The FTSE 100 firm reported net losses of 3.7 billion dollars (£2.8 billion) in 2025 due largely to the massive impairment charge on De Beers, which marked its third such write down in three years.

On an underlying basis, Anglo’s earnings edged 2% higher to 6.4 billion dollars (£4.8 billion).

Anglo has been trying to sell De Beers – in which it has an 85% stake – due to a lengthy downturn in the diamond market and amid the rise in synthetic lab-grown diamonds.

Anglo boss Duncan Wanblad said the firm is ‘progressing the separation of De Beers’ (PA)

Annual figures showed underlying losses at De Beers widened to 511 million dollars (£380 million) from 25 million dollars of losses (£19 million) in 2024 as it said “rough diamond trading conditions remained challenging”.

It cut its diamond production by 12% last year.

The latest write downs follow impairments of 2.9 billion dollars (£2.2 billion) and 1.6 billion dollars (£1.2 billion) in 2024 and 2023 respectively.

Chief executive Duncan Wanblad said in full-year results that the firm was “progressing the separation of De Beers”.

Anglo is preparing to merge with Canada’s Teck Resources in a mammoth 50 billion dollar (£37.2 billion) merger between the mining groups.

The deal will create one of the world’s largest copper producers, with the combined firm becoming Anglo Teck.

The deal received shareholder approval at the end of December and the firms are working to secure regulatory approval in different jurisdictions over the course of 2026.