Herkimer Diamond Sterling Silver EarringsTwo naturally faceted quartz crystals, each doubly terminated, set in sterling silverthe geometry is the stone's own work. Herkimer diamonds are doubly terminated quartz crystals found in Cambrian age dolostone in Herkimer County, New York. They are not diamondsthey are quartz, silicon dioxide, Mohs 7but they grow to a natural double termination within their host rock cavities, producing the pointed at both ends form typically achieved only by