metamorphic
Gneissic Schist
Gneiss-schist (Metamorphic rock)
Hardness: 6-7 (Mohs); Color: Dark gray to charcoal with light banding; Luster: Pearly to sub-metallic due to mica; Structure: Foliated; Cleavage: Good along schistosity planes; Specific Gravity: 2.7-3.0.
- Hardness
- 6-7 (Mohs)
- Color
- Dark gray to charcoal with light banding
- Luster
- Pearly to sub-metallic due to mica
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Physical properties
Hardness: 6-7 (Mohs); Color: Dark gray to charcoal with light banding; Luster: Pearly to sub-metallic due to mica; Structure: Foliated; Cleavage: Good along schistosity planes; Specific Gravity: 2.7-3.0.
Formation & geological history
Formed through the regional metamorphism of sedimentary or igneous rocks (protoliths) under high temperature and pressure conditions, typically during mountain-building events (orogenies).
Uses & applications
Used primarily in construction as crushed stone or landscaping material. Higher quality slabs are used as decorative stone or flooring.
Geological facts
The banding seen in this specimen is known as gneissic foliation, caused by the segregation of light and dark minerals during intense metamorphic squeezing.
Field identification & locations
Identify by looking for parallel layering (foliation) and a slight shimmer from mica minerals. Common in riverbeds and mountainous terrains worldwide.
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