metamorphic
Amphibolite
Amphibolite (rich in amphibole and plagioclase feldspar)
Hardness: 6 to 7 on Mohs scale; Color: Dark green, black, or brown with speckles of white or gray; Luster: Vitreous to pearly; Crystal structure: Monoclinic/Orthorhombic; Specific gravity: 2.85 to 3.3
- Hardness
- 6 to 7 on Mohs scale
- Color
- Dark green, black, or brown with speckles of white or gray
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6 to 7 on Mohs scale; Color: Dark green, black, or brown with speckles of white or gray; Luster: Vitreous to pearly; Crystal structure: Monoclinic/Orthorhombic; Specific gravity: 2.85 to 3.3
Formation & geological history
Formed under high temperature and moderate pressure conditions during regional metamorphism of mafic igneous rocks like basalt or gabbro, or from the metamorphism of clay-rich sedimentary rocks.
Uses & applications
Used in the construction industry for road stone, railroad ballast, and as a decorative stone in architecture. Due to its durability, it is often used as a dimension stone for floor tiles and cladding.
Geological facts
Amphibolite is a major component of the Earth's lower crust. It is often used as a 'pathfinder' rock to identify high-grade metamorphic zones in geological mapping.
Field identification & locations
Identified in the field by its dark, often 'salt and pepper' appearance and slight foliation. Commonly found in mountain belts (orogenic belts) and Precambrian shield areas like the Canadian Shield or the Appalachians.
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