igneous
Iron-stained quartz-rich cobble, possibly weathered granite or quartz vein rock
Quartz–feldspar aggregate with iron-oxide staining; exact classification is uncertain from the photograph
AI-generated identification · may be incorrectCoarse, rounded specimen with pale quartz/feldspar-like grains and rusty red-brown iron oxides (hematite/goethite); likely Mohs 6–7, vitreous to dull luster, massive texture, no obvious cleavage, and specific gravity roughly 2.6–2.7.
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Physical properties
Coarse, rounded specimen with pale quartz/feldspar-like grains and rusty red-brown iron oxides (hematite/goethite); likely Mohs 6–7, vitreous to dull luster, massive texture, no obvious cleavage, and specific gravity roughly 2.6–2.7.
Formation & geological history
Probably a glacially or stream-rounded fragment of felsic igneous rock or quartz vein material, later weathered and stained by oxidizing groundwater; its age cannot be determined visually.
Uses & applications
Usually a natural curiosity, landscaping stone, or teaching specimen; it has little jewelry or industrial value unless cutting reveals attractive quartz patterns.
Geological facts
The reddish-brown coloration is typically produced when iron-bearing minerals oxidize, much like rust. The smooth shape indicates prolonged transport or abrasion.
Field identification & locations
Look for glassy quartz, blocky feldspar, granular texture, and rusty coatings; acid testing is generally nonreactive. Common in stream gravels, glacial deposits, and weathered outcrops worldwide.
