metamorphic
Mica Schist
Mica Schist (KAl2(AlSi3O10)(OH)2 / K(Mg,Fe)3AlSi3O10(OH)2)
Hardness: 3.5–4 on the Mohs scale; Color: Silver, grey, or brownish-white; Luster: Pearly to sub-metallic (silvery sheen); Structure: Schistose foliation with visible flakes; Cleavage: Perfect basal cleavage in individual mica grains; Specific Gravity: 2.7–2.8
- Hardness
- 3
- Color
- Silver, grey, or brownish-white
- Luster
- Pearly to sub-metallic (silvery sheen)
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Physical properties
Hardness: 3.5–4 on the Mohs scale; Color: Silver, grey, or brownish-white; Luster: Pearly to sub-metallic (silvery sheen); Structure: Schistose foliation with visible flakes; Cleavage: Perfect basal cleavage in individual mica grains; Specific Gravity: 2.7–2.8
Formation & geological history
Formed through medium-grade regional metamorphism of clay-rich sedimentary rocks (shales or mudstones) under high pressure and temperature. Mostly associated with orogenic (mountain-building) events across various geological eras from Precambrian to Cenozoic.
Uses & applications
Used primarily as decorative stone, in garden landscaping, and as a filler in construction materials. Highly metamorphic specimens containing garnet are sometimes valued by collectors.
Geological facts
The word 'schist' is derived from the Greek 'schistos' meaning 'easily split', referring to how the rock can be cleaved into thin plates. It characterizes 'The Golden Gate' in some geological formations due to its high reflectivity.
Field identification & locations
Identify in the field by its distinct 'glittery' appearance and foliated layers that split easily. Common in mountain ranges such as the Appalachians, Alps, and Himalayas. Collectors look for accessory minerals like garnet or staurolite embedded within the mica layers.
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