Schist

Physical Properties

Hardness: 3.5-4; Color: Silvery grey to brown with distinctive glittering surface; Luster: Pearly to sub-metallic (shimmering); Crystal structure: Foliated (schistosity); Cleavage: Perfect basal cleavage in individual mica grains; Specific gravity: 2.7-2.8

Formation & Geological History

Formed through the regional metamorphism of shale or mudstone under high pressure and temperature conditions, typically during mountain-building events. Geological age varies but occurs in Precambrian to Mesozoic terranes.

Uses & Applications

Used primarily as decorative stone for garden walls, flagstones, or as a source of industrial micas. In historical times, used for building slate-like roofing if finely foliated.

Geological Facts

Schist is characterized by having more than 50% platy and elongated minerals oriented in the same direction. The term 'schist' is derived from the Greek word 'schízein', meaning 'to split'.

Field Identification & Locations

Identify in the field by its 'shimmer' when rotated in sunlight and its tendency to split into thin flakes or plates. Commonly found in metamorphic mountain belts like the Appalachians or Alps.

Identified on: 4/15/2026

Mode: Standard