metamorphic
Quartz-rich metamorphic rock (likely mica schist or gneiss)
Quartz–feldspar–mica assemblage; probable biotite schist/gneiss
AI-generated identification · may be incorrectMostly milky quartz and pale feldspar with dark biotite or amphibole patches and minor iron-oxide staining. Quartz has Mohs hardness 7 and vitreous luster; the rock is coarse-grained, with weak foliation or compositional banding visible.
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Physical properties
Mostly milky quartz and pale feldspar with dark biotite or amphibole patches and minor iron-oxide staining. Quartz has Mohs hardness 7 and vitreous luster; the rock is coarse-grained, with weak foliation or compositional banding visible.
Formation & geological history
Formed when quartz- and feldspar-bearing sediment or igneous rock was buried and recrystallized under heat and pressure, typically during regional mountain-building; age cannot be determined from the photograph. The rounded shape indicates later stream or glacial transport.
Uses & applications
Used locally as decorative stone, landscaping material, aggregate, and educational specimens; attractive pieces may be polished, though this example has limited gem value.
Geological facts
The white material is likely quartz and feldspar, while black grains may be biotite mica or amphibole; rusty brown areas are probably weathered iron-bearing minerals.
Field identification & locations
Common in eroded metamorphic terrains worldwide, including the Appalachians, Canadian Shield, and mountain belts. Look for interlocking grains, quartz-rich hardness, mica flakes, and foliation; a streak or thin-section test would improve identification.
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