Schist (Garnet-Mica Schist)
Mica Schist (Medium-grade Metamorphic Rock) · Mineral Specimen / Metamorphic Rock
Crystal System
Monoclinic (Micas) or Cubic (Garnets) with foliated/schistose texture
Mineral Group
Silicates (Phyllosilicates and Nesosilicates)
Chemical Formula
K(Al,Fe,Mg)3AlSi3O10(OH)2 (Muscovite/Biotite) + (Mg,Fe)3Al2(SiO4)3 (Garnet)
Formation Process
Metamorphic: Forms from medium-grade metamorphism of shale or mudstone under high pressure and temperature (300-500°C).
About This Crystal
A foliated metamorphic rock characterized by platelike minerals. The specimen shows a sparkling, lepidoblastic texture with visible grains of mica. Color ranges from silvery-grey to earthy brown due to iron oxidation.
Physical Characteristics
Color: Bronzy-brown to grey; Streak: White; Cleavage: Perfect basal cleavage in individual mica grains; Fracture: Uneven; Luster: Pearly to sub-metallic; Specific Gravity: 2.7-3.0.
Optical Properties
Individual mica flakes are weakly pleochroic; non-transparent; surface exhibits high reflectivity (glitter) due to the alignment of mica sheets.
Hardness & Durability
Origin Region
Global distribution; common in Appalachian Mountains (USA), Scottish Highlands, and the Alps.
Hardness & Durability
Mohs Scale: 3.5 to 4.0 for the schist matrix; tough but prone to flaking or scaling along foliation planes.
Care & Maintenance
Store in a dry area; avoid mechanical stress which causes flaking; clean only with a soft, dry brush as water may penetrate layers.
Rarity & Value
Very Common; primarily valued as geological specimens or building cladding; low financial value unless containing high-quality gemstone inclusions.
Special Characteristics
Exhibits strong foliation and 'schistosity'; often contains porphyroblasts of other minerals like garnet, staurolite, or kyanite.
Lore & History
Historically used as a building material and decorative stone; in metaphysical lore, it is associated with transition, mental clarity, and shedding outdated skin.