metamorphic
Weathered quartz-rich pebble, possibly chalcedony or quartzite
Microcrystalline quartz (SiO₂), or quartzite dominated by quartz
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; pale gray-blue, white, and tan weathering rind; dull to waxy luster with a fine-grained, massive texture and no obvious cleavage. The rounded, water-worn shape and fracture-like edge are consistent with natural silica-rich stone.
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Physical properties
Hardness about 6.5–7 Mohs; pale gray-blue, white, and tan weathering rind; dull to waxy luster with a fine-grained, massive texture and no obvious cleavage. The rounded, water-worn shape and fracture-like edge are consistent with natural silica-rich stone.
Formation & geological history
Likely formed as silica-rich material in a vein, chert-like deposit, or quartzite source rock, then rounded by erosion and weathering; its precise geological age cannot be determined from the image. The brown exterior reflects surface oxidation, soil staining, or weathering.
Uses & applications
Common pieces have little commercial use, though quartzite is used as aggregate, building stone, and decorative material; attractive translucent chalcedony can be cut or polished for cabochons and specimens.
Geological facts
The bluish appearance may result from fine inclusions, surface moisture, or lighting rather than a distinct blue mineral. A glass-scratch test can help distinguish quartz-rich rock from softer look-alikes.
Field identification & locations
Likely locations include stream beds, beaches, glacial deposits, and weathered quartz veins worldwide. Confirm with a hardness test, translucent edges, and lack of reaction to dilute hydrochloric acid; exact identification requires a fresh surface or laboratory testing.
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