metamorphic
Mica Schist with Garnet
Garnetiferous Mica Schist
Hardness: 6-7.5 (Garnet crystals), 2-3 (Mica matrix); Color: Silvery-gray, brownish-green with dark red/black spots; Luster: Pearly to Vitreous; Crystal structure: Monoclinic and Isometric grains; Cleavage: Perfect basal cleavage in mica; Specific gravity: 2.8-3.2
- Hardness
- 6-7
- Color
- Silvery-gray, brownish-green with dark red/black spots
- Luster
- Pearly to Vitreous
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Physical properties
Hardness: 6-7.5 (Garnet crystals), 2-3 (Mica matrix); Color: Silvery-gray, brownish-green with dark red/black spots; Luster: Pearly to Vitreous; Crystal structure: Monoclinic and Isometric grains; Cleavage: Perfect basal cleavage in mica; Specific gravity: 2.8-3.2
Formation & geological history
Formed through the regional metamorphism of clay-rich sedimentary rocks (pelites) under intermediate to high temperatures and pressures. Most common in mountain-building belts from various geological ages.
Uses & applications
Primarily used as a decorative stone, in construction as fill or base material, and occasionally processed for garnet abrasives used in waterjet cutting.
Geological facts
The presence of garnet in schist is a geological indicator of the intense pressure and temperature conditions the rock endured during the formation of mountain chains like the Appalachians or Himalayas.
Field identification & locations
Identify by its 'schistose' texture (layered appearance) and the sparkling, flaky mica grains. Often found in metamorphic terrains such as parts of New England or the Blue Ridge Mountains.
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