metamorphic
Weathered quartz-bearing metamorphic rock, likely gneiss or schist
Quartz–feldspar–mica rock; exact classification is uncertain from the photograph
AI-generated identification · may be incorrectLight gray, rounded, and strongly weathered, with white translucent quartz/feldspar and dark mica or other mafic grains; vitreous to dull luster. Quartz has Mohs hardness 7, while feldspar is about 6; visible foliation appears weak or obscured.
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Physical properties
Light gray, rounded, and strongly weathered, with white translucent quartz/feldspar and dark mica or other mafic grains; vitreous to dull luster. Quartz has Mohs hardness 7, while feldspar is about 6; visible foliation appears weak or obscured.
Formation & geological history
Likely formed when quartz- and feldspar-rich sediment or igneous rock underwent regional metamorphism, then was eroded into a rounded cobble. Its geological age cannot be determined visually and may range from Precambrian to much younger.
Uses & applications
Ordinary specimens are used as aggregate, riprap, and landscaping stone; attractive polished pieces may be decorative, but this specimen has limited commercial use.
Geological facts
The rounded shape indicates transport by water, ice, or coastal abrasion. Yellow-brown patches are probably iron-oxide weathering, while greenish areas may represent altered mica or chlorite.
Field identification & locations
Look for interlocking quartz/feldspar grains, mica-rich dark streaks, and any planar foliation; a streak, hardness, and acid test would help distinguish it from quartzite, granite, or concrete. Common in glacial deposits, river gravels, and metamorphic terrains.
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