London-based mining company Gemfields says it has increased production and lowered costs at its ruby mine in the northern Mozambican district of Montepuez.

In the company’s annual results for the year ended June 30, 2016, released Monday, it was revealed that Gemfields produced 10.3 million carats of ruby and corundum compared with 8.4 million carats the previous year.

During the period, this produced revenue of 73.1 million US dollars with an average price of 45.50 USD per carat. Additionally, there has been a 68 per cent increase in higher quality rough rubies discovered.

According to a company statement, production costs at the mine have been reduced marginally to 2.54 USD per carat from 2.57 USD the previous year. The company estimates that the mine holds probable ore reserves of 432 million carats, with the life of the mine put at 21 years.

Gemfields promotes itself as the world’s leading supplier of “responsibly extracted coloured gems”. It has specialised in Zambian emeralds and amethysts but has branched out into Mozambican rubies. So far, it has held six auctions of Montepuez rubies which have netted a total of 195 million USD.

Gemfields holds 75 per cent of the shares in Montepuez Ruby Mining Ltd. The other 25 per cent are owned by the Mozambican company, Mwiriti.