igneous
Tumbled blue-gray stone, likely quartzite or fine-grained basalt
Provisional identification: quartzite (mostly quartz, SiO₂) or basalt (plagioclase–pyroxene); image alone cannot distinguish reliably
AI-generated identification · may be incorrectSmooth, rounded, opaque blue-gray pebble with dull to weakly satiny luster and no visible crystals or cleavage; estimated Mohs hardness 6–7 if quartzite, or 5–6 if basalt. Specific gravity is approximately 2.7–3.0.
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Physical properties
Smooth, rounded, opaque blue-gray pebble with dull to weakly satiny luster and no visible crystals or cleavage; estimated Mohs hardness 6–7 if quartzite, or 5–6 if basalt. Specific gravity is approximately 2.7–3.0.
Formation & geological history
If quartzite, it formed when quartz-rich sandstone was metamorphosed under heat and pressure; if basalt, it solidified rapidly from mafic lava. The specimen is likely geologically ancient, but its age cannot be determined visually.
Uses & applications
Suitable for decorative stone, lapidary tumbling, crafts, and aggregate; it has little commercial gemstone value unless it displays unusual color or pattern.
Geological facts
The uniform blue-gray color and rounded shape may result from natural weathering followed by human tumbling. A streak, hardness, density, and close inspection of texture would improve identification.
Field identification & locations
Common as stream gravel, glacial material, or landscaping stone worldwide. Test whether it scratches glass: quartzite generally does, while basalt commonly does not; avoid relying on color alone.
