De Beers reveals more facets of its business

London

DE Beers, the diamond producer that's made secrecy a cornerstone of its business for more than 120 years, is pulling back the curtain to help bring more lustre to its owner Anglo American plc.

Anglo, a London-based miner of copper, coal and iron ore, hosted a 90-minute presentation for investors and analysts on Monday that revealed information De Beers has never made public before: where its best diamonds come from and how much they fetch per carat, for example.

Providing a better view of the diamond unit, acquired from the billionaire Oppenheimer family i…