Schist (specifically Chlorite/Greenschist)

Physical Properties

Hardness: 2-3.5 (Mohs scale), Color: Dirty green to grey-green, Luster: Pearly to sub-metallic on foliation planes, Crystal structure: Platy/Foliated, Cleavage: Excellent in one direction (slaty/schistose cleavage)

Formation & Geological History

Formed through low-to-medium grade regional metamorphism of clay-rich sedimentary rocks (pelites) or mafic igneous rocks under high pressure and temperature. Most commonly found in orogenic (mountain-building) belts.

Uses & Applications

Used primarily in construction for decorative stone, flagstone, and garden walls. Some varieties with unique colors are used for lapidary work or interior tiling. Historically used for roofing and writing slates.

Geological Facts

Schist is characterized by 'schistosity,' which refers to the alignment of platy grains (mica or chlorite) large enough to be seen with the naked eye. The term comes from the Greek word 'schizein', meaning 'to split'.

Field Identification & Locations

Identify in the field by its distinct layered (foliated) appearance and the presence of visible mica-like flakes that sparkle when turned in the light. It often feels slightly soapy or waxy if chlorite content is high. Commonly found in metamorphic terrains like the Appalachians or the Alps.

Identified on: 4/20/2026

Mode: Standard