igneous
Weathered quartz-rich rock, possibly granite or quartzite
Indeterminate; likely quartz–feldspar aggregate, possibly altered granite
AI-generated identification · may be incorrectHardness approximately 6–7 Mohs; cream, tan, gray, and rusty-brown colors with a dull to slightly glassy luster. Irregular massive texture and apparent quartz/feldspar grains; no diagnostic cleavage is visible.
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Physical properties
Hardness approximately 6–7 Mohs; cream, tan, gray, and rusty-brown colors with a dull to slightly glassy luster. Irregular massive texture and apparent quartz/feldspar grains; no diagnostic cleavage is visible.
Formation & geological history
Likely formed as an intrusive felsic igneous rock, then fractured and chemically weathered, producing iron-oxide staining. Exact geological age and rock identity cannot be determined reliably from the photograph alone.
Uses & applications
Comparable granite is used for construction aggregate, monuments, countertops, and dimension stone; quartz-rich pieces are mainly collected as field specimens. This individual has little commercial value.
Geological facts
The brown coloration is commonly caused by oxidation of iron-bearing minerals along fractures and weathered feldspar. A fresh broken surface, streak, and acid test would help distinguish granite from quartzite or weathered feldspathic rock.
Field identification & locations
Look for visible interlocking quartz and feldspar grains, with quartz appearing gray/glassy and feldspar opaque, often showing cleavage. Commonly found in weathered continental crust; estimated value is about $1–$10 as an ordinary specimen.
