metamorphic
Garnet Amphibolite (or Garnet Gneiss)
Garnet amphibolite / Garnet-bearing metamorphic rock
Hardness: 6-7.5 overall (garnets 6.5-7.5, quartz/feldspar 6-7, hornblende 5-6). Color: Mottled white, grey, black, with reddish-brown garnet crystals. Luster: Vitreous to sub-metallic. Texture: Coarse-grained metamorphic fabric.
- Hardness
- 6-7
- Luster
- Vitreous to sub-metallic
Identified More metamorphic →
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Physical properties
Hardness: 6-7.5 overall (garnets 6.5-7.5, quartz/feldspar 6-7, hornblende 5-6). Color: Mottled white, grey, black, with reddish-brown garnet crystals. Luster: Vitreous to sub-metallic. Texture: Coarse-grained metamorphic fabric.
Formation & geological history
Formed via regional metamorphism under high-pressure and high-temperature conditions deep within continental crust or subduction zones, converting mafic igneous or sedimentary precursor rocks into garnet-bearing amphibolite or gneiss.
Uses & applications
Used primarily as decorative river stones, landscaping rock, dimension stone, and for educational or mineral collecting purposes.
Geological facts
The deep reddish-brown mineral specks embedded throughout this rounded pebble are almandine garnets, set within a matrix of quartz, feldspar, and dark amphibole (hornblende).
Field identification & locations
Look for rounded river pebble textures showing distinct reddish-brown garnet crystals set within alternating light (feldspar/quartz) and dark (amphibole/biotite) metamorphic mineral zones. Commonly found in glacial drift, riverbeds, and metamorphic terranes like the Canadian Shield or Appalachian region.
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