Pegmatites are known to contain aquamarine, tourmaline, beryl, topaz, cassiterite, fluorite, apatite, tin and tungsten plus a host of other minerals. Minerals formed in pegmatites literally had the time to enjoy the benefits of a slow crystallization process from a rich chemical stew. One of the most common indicators of a potential pegmatite is the presence of an aplite dike. The pegmatite bodies occur as lenses within the aplite dike structures. Where other minerals such as garnet occur they are the result of a secondary metamorphic process, i.e. one where temperature and pressure have altered the original deposit.
Pegmatites are most famous for their large, high quality mineral specimens.
The first gem tourmaline discovered in California goes back to 1872 when Henry Hamilton found and recognized the mineral during a collecting trip to the southeast slope of Thomas Mountain in Riverside County. This fact was unrecorded for several years since the occurrence was not made public even to the California State Mining Bureau. The major pegmatite districts of California are the Mesa Grande District, Pala District, Ramona District, Coahuilla District, Rincon District, Ramona District, and Jacumba District. To find out more specifics about what was found in these areas to start a collection or to possibly collect you might want to sign up for the Minerals of California Online Database. Click here to sign up.