Mica Schist

Physical Properties

Hardness: 3.5-4 (Mohs); Color: Silvery-gray to brownish-gold; Lustre: Pearly to metallic (highly reflective); Crystal Structure: Foliated/platy; Cleavage: Perfect basal cleavage in individual mica grains; Specific Gravity: 2.7-3.0.

Formation & Geological History

Formed through regional metamorphism of shale, siltstone, or clay-rich sedimentary rocks under medium pressure and temperature. It is a product of the transition from phyllite to gneiss.

Uses & Applications

Used as a decorative building stone, in landscaping, and sometimes as a source of mica for industrial insulation and cosmetics (ground mica for shimmer). Not suitable for heavy construction due to its tendency to flake.

Geological Facts

Schist is characterized by 'schistosity,' which refers to the alignment of mineral grains that causes the rock to split into thin layers. The word comes from the Greek 'schizein,' meaning 'to split.'

Field Identification & Locations

Identified by its distinctive sparkly sheen (glitter-like) and flaky, layered surface. Common in mountain ranges and old metamorphic belts like the Appalachians or the Alps. For collectors, look for specimens containing garnets, which often grow within the schist matrix.

Identified on: 4/18/2026

Mode: Standard