metamorphic
Rounded quartz-rich pebble
Likely quartzite or quartz-rich metamorphic rock; exact identification requires testing
AI-generated identification · may be incorrectTan-gray, fine- to medium-grained, dull to slightly sparkly surface with rounded water-worn form; likely Mohs hardness 6.5–7, no obvious cleavage, and specific gravity about 2.6–2.7. The pale grains and possible quartz sparkle are consistent with quartzite, though weathered sandstone is also possible.
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Physical properties
Tan-gray, fine- to medium-grained, dull to slightly sparkly surface with rounded water-worn form; likely Mohs hardness 6.5–7, no obvious cleavage, and specific gravity about 2.6–2.7. The pale grains and possible quartz sparkle are consistent with quartzite, though weathered sandstone is also possible.
Formation & geological history
If quartzite, it formed when quartz sandstone was recrystallized under heat and pressure, commonly during regional mountain-building; its age cannot be determined from the image. The current rounded shape reflects erosion and transport in a river, beach, or gravel deposit.
Uses & applications
Suitable as a decorative pebble, landscaping stone, or lapidary material; quartzite is also used as aggregate and dimension stone. This individual piece has little commercial value unless it displays unusual color or texture.
Geological facts
Quartz-rich rocks commonly resist weathering, allowing them to survive transport as rounded cobbles. A glass-scratch test can help confirm quartz hardness, though it may damage the specimen.
Field identification & locations
Common in streambeds, beaches, glacial deposits, and quartzite-bearing terrains worldwide; inspect for interlocking quartz grains and test whether it scratches glass. Value is typically $1–$10 for a common collected pebble, or $10–$30 if polished or unusually attractive.
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