Schist

Physical Properties

Hardness: 3.5-4 Mohs; Color: Grey, green, or silvery; Luster: Pearly to sub-metallic due to mica; Crystal Structure: Foliated (schistosity); Cleavage: Perfect mica basal cleavage on microscopic levels; Specific Gravity: 2.7-2.8

Formation & Geological History

Formed from regional metamorphism of shale or mudstone under intermediate pressure and temperature conditions. It typically dates to mountain-building (orogenic) events across various geological eras.

Uses & Applications

Used primarily as decorative stone, construction aggregate, and occasionally in landscaping surfaces like flagstone.

Geological Facts

The word 'schist' is derived from the Greek 'schizein', meaning 'to split', referring to the rock's ease of splitting along its foliated planes of mica minerals.

Field Identification & Locations

Identify in the field by looking for a characteristic 'glittery' sheen and thin, wavy layers (foliation). It is commonly found in metamorphic terranes like the Appalachian or Himalayan mountain ranges.

Identified on: 4/20/2026

Mode: Standard