The world's biggest diamond mine is closing after almost four decades

Argyle is best known as the source of about 90% of the world's prized pink diamonds

The world’s biggest diamond mine — famed more for the fistful of coveted pink and red gems it yields each year than being a major producer of lower-quality stones — is being shuttered by Rio Tinto Group after almost four decades. Rivals from Russia to Canada hope that can help turn around the beleaguered industry.

Rio’s Argyle mine in remote Western Australia has transformed the sector since 1983 when the operation began supplying gems for both ends of the market. RBC Capital Markets and Panmure Gordon are among brokers, banks and competitors forecasting the closure could kick-start prices that have waned