Diamonds are supposed to be rare. FRONTLINE follows writer Edward Jay Epstein as he digs into that assumption and finds warehouses of uncut stones sitting on the actual truth: diamonds are common, and their price is not. The film traces how the Oppenheimer family of South Africa built and ran a cartel that controlled diamond mining, sorting, and distribution for most of the twentieth century, buying up new discoveries specifically to keep them off the market and prop up prices. Archival footage and interviews lay out the advertising campaign that turned a plentiful mineral into the required proof of love, timed so that Valentine's Day became second only to Christmas for diamond gift-giving. The film treats the industry less as a natural market than as a managed illusion, engineered decade by decade through supply control on one end and marketing on the other. It ends less concerned with geology than with the mechanics of manufactured scarcity, and what it takes to convince millions of buyers that a common stone is precious.