The Gem Deposits of Southern California

On a warm June day nearly 76 years ago, Henry Hamilton was picking his way along the brushy southeastern slope of Thomas Mountain in the Coahuila district of, southern California's Riverside County. As he crossed a small gullied area, he noticed several rough mineral fragments of attractive pink and green color. Carefully tracing the occurrence of this loose "float" material to its source higher on the hill, he encountered a ledge of light gray rock in which a few irregular cavities were lined with crystals of quartz and other minerals. Among these others were beautifully transparent pencil-like crystals of red, pink, green, and blue color. These constituted the first California discovery of gem tourmaline, a material that already had been mined in eastern parts of the United States.