igneous
Rounded quartz-rich river pebble
Quartz (SiO₂), likely derived from quartzite or granitic rock
AI-generated identification · may be incorrectGray-white, translucent to opaque, with a vitreous to weathered luster and no obvious cleavage; quartz has hardness 7, while the rounded surface reflects abrasion. The specimen appears fine- to medium-grained and may contain minor feldspar or iron staining.
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Physical properties
Gray-white, translucent to opaque, with a vitreous to weathered luster and no obvious cleavage; quartz has hardness 7, while the rounded surface reflects abrasion. The specimen appears fine- to medium-grained and may contain minor feldspar or iron staining.
Formation & geological history
Produced by weathering and transport in a stream or beach environment; abrasion rounded the pebble. Its original rock may be Precambrian to younger quartzite or granite, but age cannot be determined from the photograph.
Uses & applications
Primarily a landscaping, craft, or teaching specimen; attractive translucent pieces may be tumbled or used in decorative work, but this example is not gem quality.
Geological facts
The rounded shape is secondary—it records transport history rather than crystal habit. Quartz commonly survives erosion because it is chemically and mechanically resistant.
Field identification & locations
Look for glassy translucence, hardness sufficient to scratch ordinary glass, and lack of acid reaction; quartzite shows interlocking grains, whereas a single quartz crystal may show conchoidal fracture. Common in river gravels worldwide.
