metamorphic
Tumbled garnet-bearing gneiss
Gneiss containing almandine–pyrope garnet, quartz, feldspar, and mica
AI-generated identification · may be incorrectTypically hardness 6–7 (garnet about 6.5–7.5); coarse, granular texture with gray-green, purple, and pink patches, glassy to dull luster, and no consistent cleavage in the whole stone. The mottled banding and dark red-purple grains are consistent with garnet-bearing metamorphic rock, though the image alone cannot confi…
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Physical properties
Typically hardness 6–7 (garnet about 6.5–7.5); coarse, granular texture with gray-green, purple, and pink patches, glassy to dull luster, and no consistent cleavage in the whole stone. The mottled banding and dark red-purple grains are consistent with garnet-bearing metamorphic rock, though the image alone cannot confirm mineral identity.
Formation & geological history
Formed when pre-existing rocks underwent high-grade regional metamorphism, commonly during mountain building; its exact geological age and locality cannot be determined visually. Rounded edges indicate natural stream wear or tumbling/polishing.
Uses & applications
Used mainly as a lapidary and collectible stone; garnet-bearing gneiss is also used locally as decorative aggregate or facing stone, but this small specimen has no industrial value.
Geological facts
Gneiss develops compositional segregation into light and dark minerals under heat and pressure; garnet crystals can survive metamorphism and record pressure-temperature conditions.
Field identification & locations
Look for planar mineral banding, granular texture, and hard, dark red-purple garnet grains that resist scratching by steel. Common sources include Norway, India, Madagascar, and the United States; confirm with a loupe, streak, and hardness tests.
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