Mica Schist

Physical Properties

Hardness: 3.5-5.5 (Mohs); Color: Silvery-gray, metallic/shiny; Luster: Pearly to Vitreous; Crystal structure: Monoclinic (plates); Cleavage: Perfect basal (flaking); Specific Gravity: 2.8-3.0.

Formation & Geological History

Formed through regional metamorphism of shale or mudstone under medium-grade pressure and temperature (300-450°C). This process causes platy minerals like mica to align, creating a foliated 'schistose' texture.

Uses & Applications

Used occasionally as decorative building stone, flagging, or for landscaping. Muscovite mica specifically is used in electrical insulation and as a glittery additive in makeup and paints.

Geological Facts

The word 'schist' is derived from the Greek word 'schizein', meaning 'to split', referring to how easily the rock can be flaked into thin plates due to its foliation.

Field Identification & Locations

Identify in the field by its distinct 'glittery' appearance and foliated layers that flake off easily with a fingernail or knife. Commonly found in core mountain ranges like the Appalachians or Alps.

Identified on: 4/21/2026

Mode: Standard