metamorphic
Schist
Schist (metamorphic rock)
Hardness: 3.5 to 5 on the Mohs scale; Color: typically gray, silvery, or brownish due to weathered iron oxides; Luster: vitreous (glassy) to earthy; Structure: foliated with distinctly visible medium-to-coarse grained minerals (schistosity); Cleavage: splits easily into thin flakes or slabs.
- Hardness
- 3
- Luster
- vitreous (glassy) to earthy
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Physical properties
Hardness: 3.5 to 5 on the Mohs scale; Color: typically gray, silvery, or brownish due to weathered iron oxides; Luster: vitreous (glassy) to earthy; Structure: foliated with distinctly visible medium-to-coarse grained minerals (schistosity); Cleavage: splits easily into thin flakes or slabs.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under intermediate to high temperatures and pressures. The minerals have aligned themselves perpendicular to the direction of pressure, creating the characteristic layered or flaky appearance.
Uses & applications
Historically used for flagstone, paving, and occasionally as a host rock for minerals like garnet or graphite. In modern times, it is used as decorative stone in construction and as part of educational rock collections.
Geological facts
Schist is characterized by its 'schistosity,' which refers to the alignment of mica flakes that allow it to be split into thin plates. It represents a higher grade of metamorphism than slate and phyllite, but a lower grade than gneiss.
Field identification & locations
Identify in the field by its distinct shiny, layered appearance and its tendency to flake or peel when struck. Common in mountain ranges and metamorphic belts globally. Collectors should look for specimens containing 'porphyroblasts' like garnet or staurolite embedded in the mica layers.
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