Mica-rich Pegmatite

Physical Properties

Hardness: 2.5-3 for mica, 6-7 for matrix; Color: Silver, gold, bronze, or black flakes with white/translucent quartz; Luster: Pearly or metallic reflections on mica faces; Crystal structure: Monoclinic (platy/foliated mica) and Hexagonal (quartz grains); Specific gravity: 2.7-3.0

Formation & Geological History

Formed during the final stage of magma crystallization where high water content allows for the growth of large, distinct crystals. Generally found in plutonic environments and associated with granitic intrusions.

Uses & Applications

Mica is used as an electrical insulator, in paints, cosmetics (glitter), and as a filler in plastics. Pegmatites are also primary sources of rare earth elements and gemstones.

Geological Facts

Mica flakes can be split into extremely thin, flexible, and transparent sheets due to their perfect basal cleavage. In ancient times, large transparent mica sheets were used as window panes.

Field Identification & Locations

Identify by looking for 'books' or stacks of shiny, flaky crystals that can be peeled with a fingernail, embedded in a coarse-grained crystalline matrix. Commonly found in mountainous regions with metamorphic or old igneous basements.

Identified on: 5/3/2026

Mode: Standard