Schist

Physical Properties

Hardness: 3.5-4; Color: Silvery-gray, brownish-gold when weathered; Luster: Submetallic, shimmering (schistose); Structure: Foliated with visible mineral grains; Cleavage: Excellent basal cleavage in mica components.

Formation & Geological History

Formed through the regional metamorphism of shale or mudstone at medium grades of pressure and temperature. Micas (muscovite/biotite) align perpendicular to pressure, creating the characteristic shine.

Uses & Applications

Used as decorative stone in architecture, garden flagstones, and historically as a medium for carving. Occasionally used for building foundations where strength is secondary to availability.

Geological Facts

The word 'schist' comes from the Greek 'schizein', meaning 'to split'. This refers to its tendency to break easily along the planes of mica alignment. It is the intermediate stage between phyllite and gneiss.

Field Identification & Locations

Identify in the field by its distinct sparkle (micaceous sheen) and visible parallel layers of minerals. It is much coarser than slate or phyllite and will flake off in thin sheets when struck.

Identified on: 4/26/2026

Mode: Standard