igneous
Granite or granitic pegmatite fragment
Felsic intrusive rock, chiefly quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, mottled tan-gray rock with visible interlocking crystals and little cleavage as a whole; constituent feldspar has Mohs hardness ~6, quartz ~7, mica ~2–3. Typically vitreous quartz, pearly mica, and earthy-to-glassy feldspar luster; specific gravity about 2.6–2.7.
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Physical properties
Coarse-grained, mottled tan-gray rock with visible interlocking crystals and little cleavage as a whole; constituent feldspar has Mohs hardness ~6, quartz ~7, mica ~2–3. Typically vitreous quartz, pearly mica, and earthy-to-glassy feldspar luster; specific gravity about 2.6–2.7.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep underground, producing the visible coarse texture. Its precise geological age cannot be determined from the photograph; granitic rocks in northwestern Russia commonly range from Precambrian to Paleozoic.
Uses & applications
Used as crushed stone, aggregate, building and paving material, and occasionally as a decorative stone. This small weathered fragment has negligible commercial or jewelry value.
Geological facts
The tan grains are probably potassium feldspar, with gray translucent quartz and dark biotite or amphibole. It may alternatively be a weathered granitic gneiss, but layering or foliation is not clear.
Field identification & locations
Commonly found in glacial tills, stream gravels, and exposed bedrock around the Vologda-region latitude. A fresh broken surface, visible quartz, feldspar, and dark mica, plus hardness sufficient to scratch glass, support granite identification; a streak or acid test is usually unhelpful.
