metamorphic
Garnet-Bearing Schist
Almandine Garnet Micaceous Schist
Hardness: 6.5-7.5 (garnets), 2-3 (mica matrix); Color: Reddish-brown crystals in a gray/silver matrix; Luster: Vitreous to sub-metallic; Structure: Foliated schistose; Cleavage: None in garnet, perfect basal in mica.
- Hardness
- 6
- Color
- Reddish-brown crystals in a gray/silver matrix
- Luster
- Vitreous to sub-metallic
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Physical properties
Hardness: 6.5-7.5 (garnets), 2-3 (mica matrix); Color: Reddish-brown crystals in a gray/silver matrix; Luster: Vitreous to sub-metallic; Structure: Foliated schistose; Cleavage: None in garnet, perfect basal in mica.
Formation & geological history
Formed during regional metamorphism of shale or mudstone under high temperature and pressure conditions, typically in mountain-building zones (orogenic belts) during the Paleozoic or Precambrian eras.
Uses & applications
Used industrially as an abrasive (sandpaper, waterjet cutting) and as a semi-precious gemstone in jewelry when crystals are large and clear. Commonly a collector's specimen.
Geological facts
Garnets are known as 'index minerals,' allowing geologists to determine the specific temperature and pressure conditions under which a rock formed. Large almandine garnets are the most common variety found in schists globally.
Field identification & locations
Identify by looking for hard, rounded reddish 'balls' embedded within a shimmering, flaky, layered rock matrix. Commonly found in metamorphic terrains like the Appalachian Mountains or the Alps.
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