(IDEX Online) - Gem Diamonds reports a slight increase in quarterly revenue, up four per cent on Q4 2021 to $52.1m, and says it is confident about future prices.Revenue for the three months to the end of March 2022 was up 19 per cent on the same quarter last year.The UK-based miner sold 28,461 carats in Q1 2022, according to a trading update, compared to 24,790 carats in the previous quarter. But per carat prices fell from $2,018 to $1,831.Gem Diamonds is 70 per cent owner of Letseng, in Lesotho, the highest dollar per carat kimberlite diamond mine in the world.Highlights of the quarter included the sale of an 8.41 carat pink diamond for over $555,000 and a Type IIa white diamond that realized $53 834 per carat. Nine diamonds sold for more than $1m each, a combined revenue of $16.2m.Clifford Elphick, Gem Diamonds' CEO, said: "We remain confident about the outlook for diamond prices, particularly for Letseng's large high-value diamonds with an average price of $1,831 per carat achieved during the period. Prices achieved on a like-for-like basis continued the largely upward trend from 2021."Pic shows rough diamonds being weighed at the Letseng mine.