metamorphic
Mica Schist (with Garnet)
Garnet-Mica Schist
Hardness: 6.5-7.5 (garnets) / 2-3 (mica matrix). Color: Silver-grey, tan, reddish-brown. Luster: Pearly to sub-metallic (mica), vitreous (garnet). Crystal structure: Monoclinic (mica), Isometric (garnet). Cleavage: Perfect basal (mica) / None (garnet).
- Hardness
- 6
- Color
- Silver-grey, tan, reddish-brown
- Luster
- Pearly to sub-metallic (mica), vitreous (garnet)
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Physical properties
Hardness: 6.5-7.5 (garnets) / 2-3 (mica matrix). Color: Silver-grey, tan, reddish-brown. Luster: Pearly to sub-metallic (mica), vitreous (garnet). Crystal structure: Monoclinic (mica), Isometric (garnet). Cleavage: Perfect basal (mica) / None (garnet).
Formation & geological history
Formed through the regional metamorphism of clay-rich sedimentary rocks like shale or mudstone under high pressure and temperature. This specimen shows a schistose texture with visible porphyroblasts.
Uses & applications
Primary collector specimens; occasionally used as a soil conditioner (vermiculite source) or for decorative stone in landscaping. Industrial garnets are used as abrasives.
Geological facts
The term 'Schist' is derived from the Greek word 'schistos', meaning 'split', referring to the ease with which the rock can be split into thin flakes along its foliation planes.
Field identification & locations
Identify by its sparkly, 'glittery' appearance caused by mica flakes and the presence of small, harder, rounded nodules (garnets). Found in mountainous regions near metamorphic belts worldwide.
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