metamorphic
Tumbled quartz-rich pebble, possibly quartzite
Quartzite (mostly SiO₂); alternatively quartz-rich sandstone
AI-generated identification · may be incorrectCream to tan, rounded and polished, with granular texture and pale brown veining. Quartz hardness is 7 Mohs; quartzite is noncleaved, typically vitreous to dull, and has specific gravity around 2.6–2.7.
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Physical properties
Cream to tan, rounded and polished, with granular texture and pale brown veining. Quartz hardness is 7 Mohs; quartzite is noncleaved, typically vitreous to dull, and has specific gravity around 2.6–2.7.
Formation & geological history
Likely formed from quartz sandstone recrystallized during metamorphism, with grains fused into a durable quartz mosaic; the exact geological age cannot be determined from the image. Its rounded shape indicates later stream or beach abrasion, followed by tumbling or natural wear.
Uses & applications
Used as aggregate, landscaping stone, decorative pebble, and occasionally lapidary material; attractive pieces may be polished for cabochons or small ornaments.
Geological facts
Quartzite commonly resists weathering better than surrounding rocks, producing rounded stream pebbles. Strong effervescence with dilute acid would suggest carbonate cement or limestone instead, not pure quartzite.
Field identification & locations
Identify by its very hard, grainy quartz texture, lack of obvious cleavage, and inability to scratch with a steel knife; quartz should scratch glass. Common in mountain belts and quartz-rich river gravels.
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