Schist/Phyllite

Physical Properties

Hardness: 3.5-4 (Mohs scale); Color: Grayish-green to silvery; Luster: Pearly or silky (foliated); Crystal structure: Monoclinic/Triclinic; Cleavage: Basal (splitting into thin sheets); Specific Gravity: 2.7-3.0

Formation & Geological History

Formed from the regional metamorphism of clay-rich sedimentary rocks (like shale) under medium pressure and heat. These pieces show typical foliated textures associated with mountain-building events.

Uses & Applications

Primary use is in construction as dimensional stone or crushed stone. Historically used for roofing or floor tiles. Low commercial value as a mineral specimen unless containing garnets.

Geological Facts

Schist is characterized by its large, platy mineral grains. These specific fragments appear to be chlorite or mica-rich, giving them the slight greenish-gray tint and plate-like structure.

Field Identification & Locations

Identify in the field by its 'schistosity'—the ability to split into thin sheets—and its characteristic sheen due to mica content. Very common in metamorphic belts and river gravel in mountainous areas.

Identified on: 4/15/2026

Mode: Standard