metamorphic
Garnet Schist
Garnetiferous Micaceous Schist
Hardness: 6.5-7.5 (garnets), 2-3 (mica matrix). Color: Silver-grey to green-grey matrix with reddish-brown almandine garnets. Luster: Vitreous garnets in a pearly/sub-metallic matrix. Structure: Foliated with visible porphyroblasts.
- Hardness
- 6
- Luster
- Vitreous garnets in a pearly/sub-metallic matrix
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7.5 (garnets), 2-3 (mica matrix). Color: Silver-grey to green-grey matrix with reddish-brown almandine garnets. Luster: Vitreous garnets in a pearly/sub-metallic matrix. Structure: Foliated with visible porphyroblasts.
Formation & geological history
Formed through regional metamorphism of clay-rich sedimentary rocks (shales) at intermediate to high temperatures and pressures. Most common in mountain-building belts of Proterozoic to Paleozoic ages.
Uses & applications
Garnets are used as industrial abrasives (sandpaper, waterjet cutting) and as gemstones. Schist itself is sometimes used for decorative stone or flagstone in landscaping.
Geological facts
The larger crystals in the rock are called porphyroblasts. The schistosity (alignment of micas) allows the rock to split easily along parallel planes.
Field identification & locations
Identified in the field by its distinct 'shimmer' or 'sparkle' due to mica and the presence of small, rounded, dark red or brown hard crystals. Commonly found in metamorphic terrains like the Appalachian or Himalayan mountains.
More like this
