metamorphic
Polished garnet-bearing metamorphic rock
Likely garnet mica schist or garnet-bearing gneiss; garnet is commonly almandine, Fe₃Al₂(SiO₄)₃
AI-generated identification · may be incorrectDark maroon-brown, irregularly polished specimen with reflective silvery mica and pale mineral veins. Garnet hardness is 6.5–7.5 Mohs; mica is softer (2–3), with vitreous to pearly luster and imperfectly visible foliation.
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Physical properties
Dark maroon-brown, irregularly polished specimen with reflective silvery mica and pale mineral veins. Garnet hardness is 6.5–7.5 Mohs; mica is softer (2–3), with vitreous to pearly luster and imperfectly visible foliation.
Formation & geological history
Formed when aluminum-rich sedimentary or igneous rocks underwent medium- to high-grade regional metamorphism, commonly during mountain building. The exact geological age cannot be determined from the photograph.
Uses & applications
Used mainly as a decorative or collecting stone; garnet may be recovered as an abrasive or gemstone, but this foliated rock is generally unsuitable for faceted jewelry or construction.
Geological facts
The red-brown areas likely contain garnet porphyroblasts, while the silvery flakes are mica. White veins may be quartz or feldspar.
Field identification & locations
Look for hard reddish garnet grains, flaky mica, and planar fabric; a steel file should scratch mica but not garnet. Common sources include metamorphic belts in India, Brazil, Madagascar, Scandinavia, and North America.
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