metamorphic
Schist
Schist (Crystalline metamorphic rock)
Hardness: 3.5-5 (variable based on mineral composition); Color: Grey, silver, or brownish-gold with metallic sheen; Luster: Pearly to sub-metallic; Crystal Structure: Medium to coarse-grained with visible 'schistosity' (foliated layers of mica); Cleavage: Perfect mica-like cleavage along foliation planes.
- Hardness
- 3
- Color
- Grey, silver, or brownish-gold with metallic sheen
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5-5 (variable based on mineral composition); Color: Grey, silver, or brownish-gold with metallic sheen; Luster: Pearly to sub-metallic; Crystal Structure: Medium to coarse-grained with visible 'schistosity' (foliated layers of mica); Cleavage: Perfect mica-like cleavage along foliation planes.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under intermediate to high temperatures and pressures. Most common in mountain belts or billion-year-old Precambrian shields.
Uses & applications
Used historically as a decorative building stone, for landscape flagstones, and as a filler in road construction. Some varieties with high garnet concentrations are mined for abrasives.
Geological facts
Schist is defined by its foliation: at least 50% of its minerals are aligned in flat, thin layers. The sparkly 'glitter' effect is caused by large flakes of muscovite or biotite mica reflecting light.
Field identification & locations
Identify in the field by its distinct 'shimmery' or glittery appearance and flaky texture that allows the rock to be split into thin plates. Commonly found in the Appalachian Mountains, Scandinavia, and the Alps.
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