When it comes to pink diamonds, there is a reliable producer and a dominant one but the diamonds are relatively small. Rio Tinto’s Argyle mine in Western Australia yields 20 million carats of diamonds in an array of brownish tones. Occasionally, a pink diamond is discovered. Josephine Johnson, manager of Argyle Pink Diamonds, says, “Less than one-tenth of 1 percent of Argyle’s production is pinks, accounting for 90 percent of the world’s supply.”

The prized pinnacle of Argyle’s production are the rare stones sold at the company’s annual Pink Diamond Tender. These intense, often purplish pink or purplish red diamonds are the glittering prizes that stand out from the mine’s more mundane production.

Argyle’s run-of-the-mine production comprises many shades of browns. Bruno Sane, Rio Tinto’s general manager of marketing, says, “Brown diamonds comprise around 70 percent of the volume of the Argyle mine.” These are the “Champagne” colours that allow the average jewellery buyer to own a piece of the colored rock.

With the shift from open pit to underground mining scheduled to be complete at Argyle by 2015, this production volume is expected to continue until “at least 2020,” according to Robyn Ellison, Rio Tinto spokesperson. She adds, “The colour, size and quality distribution of Argyle diamonds does not change as the mine goes deeper.”

In the coming years, Rio Tinto will assess the economics of continuing to mine for these small, various-colored diamonds. Having single-handedly made a market for the gems, Rio Tinto virtually invented — and branded — a new jewellery category for diamonds in colours that were not even used previously. It would be difficult to assess the impact the loss of these diamonds would have on the jewellery market. For example, the firm’s greyish production, dubbed “Silvermist,” is sold across the United States at Sam’s Club stores. Not since De Beers invented the diamond engagement ring market had another miner found a way to create a category for its production.

Historically, the Williamson mine in Tanzania was known for “bubblegum” pinks but, according to Dippenaar, who says he purchased that mine two years ago, “We’ve treated 7 million tons of ore and haven’t had a pink of consequence” in all that time. Petra’s Koffiefontein mine, which the firm bought from De Beers in 2007, has produced a 6-carat pink. Pinks are found sporadically in mines across the globe, including light pink from Brazil, as well as green stones with a somewhat oily appearance. The occasional purple diamond surfaces in Siberia.