pegmatite (redirected from Pegmatites)

pegmatite: see granite.

---

pegmatite

Almost any wholly crystalline igneous rock that is at least in part very coarse-grained, the major constituents of which include minerals typically found in ordinary igneous rocks (such as granites) and in which extreme textural variations, especially in grain size, are characteristic. Usually found as irregular dikes, lenses, or veins, pegmatite deposits occur in all parts of the world and are the chief source of commercial feldspar, sheet mica, and beryllium, tantalum-niobium, and lithium minerals.

---

pegmatite [′peg·mə‚tīt]

(petrology)

Any extremely coarse-grained, igneous rock with interlocking crystals; pegmatites are relatively small, are relatively light colored, and range widely in composition, but most are of granitic composition; they are principal sources for feldspar, mica, gemstones, and rare elements. Also known as giant granite; granite pegmatite.