igneous, sedimentary, metamorphic

Mixed river-worn rock collection

Uncertain; likely quartzite, sandstone, basalt, and weathered granite or gneiss

AI-generated identification · may be incorrect

Rounded cobbles with gray, tan, pink, blue-gray, and reddish colors; mostly dull to slightly silky luster, massive textures, and no obvious cleavage. Likely hardness ranges from Mohs 5–7, with quartz-rich pieces hardest; exact identification requires tests such as streak, acid reaction, and magnification.

Identified August 15, 2026More igneous, sedimentary, metamorphic →

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At a glance

Common name: Mixed river-worn rock collection
Scientific name: Uncertain; likely quartzite, sandstone, basalt, and weathered granite or gneiss
Category: igneous, sedimentary, metamorphic
Identified: August 15, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 per common cobble; polished, unusual, or demonstrably local specimens may sell for approximately $10–$50.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

These are probably glacial or stream-transported cobbles, rounded by abrasion and weathering; their ages depend on source bedrock and may range from millions to billions of years. The pink specimen may be iron-stained sandstone or feldspathic rock, while the dark gray pieces may be basalt or quartzite.

Uses & applications

Commonly used for landscaping, garden decoration, drainage, aquarium décor, craft projects, and educational collections; attractive pieces may be polished or cut.

Geological facts

The visible white patches could be quartz or feldspar, whereas the speckled gray cobbles may contain mafic minerals. Surface color alone is insufficient for reliable species identification.

Field identification & locations

Look for grain size, layering, foliation, visible crystals, and acid fizz; a glass scratch test can distinguish quartz-rich rocks from softer materials. Such rounded cobbles are common in riverbeds, beaches, and glacial deposits worldwide.