(IDEX Online) - Gem Diamonds reported increased sales after its Letseng mine resumed operations and demand for its diamond improved.The London-based miner was hard hit by the coronavirus pandemic and in September it said revenue had slipped from $93.1m in H1 of 2019 to $69.5m.But today's Q3 2020 trading update shows positive cash flow, revenue of $25.6m and much-reduced debt.It achieved higher per-carat prices - $2,215 per carat, up from $1,714 per carat in H1 - and sold seven stones for over $1m each.The mine was closed between March and May by the global pandemic.CEO Clifford Elphick said: "These prices achieved (on a like for like basis) are higher than those realised in the pre Covid-19 market conditions of H2 2019. "This, together with the continued pro-active cost control and cash preservation measures implemented across the group, has resulted in continued positive cash flow."Gem operates the highest dollar per carat kimberlite diamond mine in the world, in landlocked Lesotho, and has just agreed a 10-year extension to its mining lease.Pic shows Letseng mine