metamorphic
Weathered gray pebble, likely quartzite or chert
Quartzite (microcrystalline SiO₂); possibly chert (cryptocrystalline SiO₂)
AI-generated identification · may be incorrectGray-tan, fine-grained, dull to weakly vitreous luster, with no visible crystals or cleavage; quartz-rich material is typically Mohs 6.5–7 and has specific gravity around 2.6. The rounded edges indicate natural abrasion or tumbling.
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Physical properties
Gray-tan, fine-grained, dull to weakly vitreous luster, with no visible crystals or cleavage; quartz-rich material is typically Mohs 6.5–7 and has specific gravity around 2.6. The rounded edges indicate natural abrasion or tumbling.
Formation & geological history
Quartzite forms when quartz sandstone is recrystallized during metamorphism; chert forms by silica precipitation or replacement in sedimentary settings. Age cannot be determined from the photograph; both occur from Precambrian to recent deposits.
Uses & applications
Common quartzite is used as aggregate, road stone, landscaping material, and occasionally decorative stone; chert is used for tools and ornamental pieces. This small specimen has minimal commercial value.
Geological facts
The specimen’s smooth, water-worn form and uniform fine texture are consistent with a stream or beach pebble. A fresh quartzite fracture is typically sugary and sparkly, while chert breaks with a smooth conchoidal fracture.
Field identification & locations
Likely found in river gravels, beaches, glacial deposits, or weathered rock outcrops. A steel nail should not scratch it; quartz-rich specimens may scratch glass, though the image alone cannot distinguish quartzite from chert confidently.
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