Schist

Physical Properties

Hardness: 3.5-4; Color: Grey, silvery-white, or black; Luster: Pearly to sub-metallic due to mica; Structure: Foliated with distinct layers (schistosity); Cleavage: Perfect mica-like cleavage on individual grains; Specific gravity: 2.5-2.9

Formation & Geological History

Formed through the regional metamorphism of shale or mudstone under intermediate to high temperatures and pressures. This creates large crystal grains of mica that align perpendicularly to the pressure direction.

Uses & Applications

Used primarily as decorative stone, in garden walling, high-quality flagstone, and occasionally as a source of industrial minerals like garnet or graphite contained within the rock.

Geological Facts

The word 'schist' is derived from the Greek word 'schízein', meaning 'to split', referring to the ease with which the rock can be split into flakes or slabs along its foliated planes.

Field Identification & Locations

Identify in the field by its distinct 'shimmer' or 'glitter' when rotated in sunlight and its tendency to flake off in thin, irregular plates. Found in mountain belts like the Appalachians or Alps.

Identified on: 4/13/2026

Mode: Standard