metamorphic
Garnet Schist
Garnet-bearing Mica Schist
Hardness: Matrix 2.5-3 (mica) and Garnet 6.5-7.5. Color: Dark gray to silver-gray background with reddish-pink garnet porphyroblasts. Luster: Vitreous to pearly matrix, sub-vitreous to vitreous garnet crystals. Cleavage: Perfect mica schistosity cleavage in matrix, garnet lacks distinct cleavage.
- Hardness
- Matrix 2
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Physical properties
Hardness: Matrix 2.5-3 (mica) and Garnet 6.5-7.5. Color: Dark gray to silver-gray background with reddish-pink garnet porphyroblasts. Luster: Vitreous to pearly matrix, sub-vitreous to vitreous garnet crystals. Cleavage: Perfect mica schistosity cleavage in matrix, garnet lacks distinct cleavage.
Formation & geological history
Formed via regional metamorphism of shale or mudstone under moderate to high temperatures and pressure deep within the Earth's crust, causing garnet porphyroblasts to grow within a foliated mica matrix.
Uses & applications
Used primarily for geological study, educational mineral collections, and decorative display specimens. Industrial garnet is harvested for abrasives and waterjet cutting.
Geological facts
Garnet schists are classic examples of metamorphic porphyroblastic textures where garnets grow larger than the surrounding matrix. Garnet serves as an index mineral to determine the metamorphic grade of the rock.
Field identification & locations
Identified by distinct reddish dodecahedral or rounded garnet crystals embedded in a shiny, foliated micaceous matrix. Commonly found in metamorphic terranes like the Scottish Highlands, the Alps, and North American Appalachian regions.
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