Quartz with mica and feldspar (Pegmatite fragment)
Granitic Pegmatite (composed mainly of SiO2 with KAlSi3O8)
Rock Type: igneous
Physical Properties
Hardness: 6-7 (Mohs); Color: White, translucent, to brownish/grey; Luster: Vitreous to pearly; Crystal structure: Hexagonal/monoclinic depending on specific mineral grains; Cleavage: None for quartz, good for mica/feldspar.
Formation & Geological History
Formed during the final stage of a magma's crystallization, usually in intrusive igneous environments. These are characterized by exceptionally large crystals due to the presence of water which helps ions migrate quickly.
Uses & Applications
Sources of industrial minerals like quartz for glass and silicon, mica for electronics and cosmetics, and feldspar for ceramics. High-quality pegmatites can yield gemstones.
Geological Facts
Pegmatites can produce the largest crystals ever found on Earth, sometimes exceeding several meters in length. This specific specimen appears to be a small chip from a larger granitic vein.
Field Identification & Locations
Identify by looking for course-grained textures (large crystals) and a mix of light-colored minerals. Commonly found in mountainous regions or areas with exposed ancient continental crust.
Identified on: 4/27/2026
Mode: Standard