mineral
Tumbled blue-gray stone, possibly chalcedony or quartzite
Likely microcrystalline quartz (SiO₂), but the image is insufficient for confident identification
AI-generated identification · may be incorrectSmooth, rounded, polished surface; blue-gray to tan coloration with a dull-to-waxy luster. Quartz-based material has Mohs hardness about 7, no visible cleavage, and specific gravity near 2.6; translucency and hardness testing would help distinguish it from glass or other stone.
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Physical properties
Smooth, rounded, polished surface; blue-gray to tan coloration with a dull-to-waxy luster. Quartz-based material has Mohs hardness about 7, no visible cleavage, and specific gravity near 2.6; translucency and hardness testing would help distinguish it from glass or other stone.
Formation & geological history
If chalcedony, it formed when silica-rich fluids filled cavities or fractures and precipitated as microcrystalline quartz, commonly in volcanic rocks. If quartzite, it is metamorphosed sandstone; age depends on its source locality.
Uses & applications
Typically used as a tumbled decorative stone, pocket specimen, or craft material; quality translucent examples may be used in inexpensive jewelry.
Geological facts
The blue-gray color may result from microscopic inclusions, staining, or surface treatment. A glassy appearance alone cannot reliably identify the material.
Field identification & locations
Common sources include Brazil, Madagascar, India, Uruguay, and the United States. Field tests: quartz should scratch glass and resist a steel knife; inspect for bubbles, which suggest glass, and use a specific-gravity or gemological test for confirmation.
