igneous
Weathered quartz-rich pebble
Likely altered granite or granitic gneiss; chiefly quartz and feldspar with minor mica/iron oxides
AI-generated identification · may be incorrectHardness about 6–7 overall; pale gray, cream, and pink, with dull to weakly vitreous luster and an irregular granular texture. No clear cleavage is visible in the rounded, weathered surface; density is typically about 2.6–2.7 g/cm³.
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Physical properties
Hardness about 6–7 overall; pale gray, cream, and pink, with dull to weakly vitreous luster and an irregular granular texture. No clear cleavage is visible in the rounded, weathered surface; density is typically about 2.6–2.7 g/cm³.
Formation & geological history
Formed from slowly cooled silica-rich magma, likely Precambrian to younger continental crust, then exposed and rounded by weathering and abrasion in a stream, beach, or glacial deposit. The dark staining may reflect iron-oxide alteration or minor biotite.
Uses & applications
Commonly used as aggregate, dimension stone, landscaping stone, and a lapidary or teaching specimen; this small unpolished piece has little commercial value.
Geological facts
Quartz grains resist weathering while feldspar alters to pale clay, producing the mottled, crumbly appearance. A fresh broken surface would reveal whether it is granite, gneiss, or another quartz-feldspar rock.
Field identification & locations
Look for interlocking quartz and feldspar grains, possible black mica, and a scratch resistance near quartz; it should scratch glass but not be scratched by a steel knife easily. Common in continental terrains worldwide, especially glaciated or mountainous regions.
