Herkimer diamonds are not true diamonds, but instead are quartz crystals which are naturally double terminated (faceted at both ends). Produced within dolomitic rock, they were discovered in and around Herkimer County in upstate New York. With their exceptionally high degree of clarity, they exhibit a diamond-like appearance. Among those that use healing crystals, Herkimer diamonds are considered to be the most powerful of the quartz crystals. 14k gold posts and backs.