metamorphic
Garnet-bearing metamorphic rock
Garnet amphibolite or garnet schist; almandine garnet (Fe₃Al₂Si₃O₁₂) likely
AI-generated identification · may be incorrectDark brown-red, granular and weakly sparkly, with a pale quartz or feldspar vein/matrix. Garnet hardness is 6.5–7.5 Mohs, vitreous luster, cubic crystal structure, and no cleavage; the host appears finer-grained and foliated.
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Physical properties
Dark brown-red, granular and weakly sparkly, with a pale quartz or feldspar vein/matrix. Garnet hardness is 6.5–7.5 Mohs, vitreous luster, cubic crystal structure, and no cleavage; the host appears finer-grained and foliated.
Formation & geological history
Likely formed when a preexisting mafic or clay-rich rock underwent medium- to high-grade regional metamorphism during mountain building. Exact geological age cannot be determined from the photograph.
Uses & applications
Common garnet-bearing rocks are mainly collector specimens and sources of abrasive garnet; attractive garnet crystals may be cut as gemstones. The host rock has limited construction use unless present in large, sound quarry material.
Geological facts
The rounded dark body may be a weathered garnet crystal rather than a whole rock, attached to lighter quartz/feldspar. Garnet is commonly identified by its lack of cleavage and resistance to scratching.
Field identification & locations
Look for red-brown, glassy grains that scratch glass and show dodecahedral or trapezohedral forms; a hand lens and streak, hardness, and density tests help distinguish garnet from mica or iron oxides. Common sources include metamorphic terrains in India, Madagascar, Sri Lanka, the United States, and Scandinavia.
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