mineral
Blue-gray chalcedony (likely common quartz/chert)
Microcrystalline quartz, SiO₂; possibly weathered chert or chalcedony
AI-generated identification · may be incorrectPale blue-gray, translucent to semi-opaque, with a waxy to dull luster and irregular conchoidal fracture; Mohs hardness about 6.5–7, no cleavage, trigonal quartz structure, specific gravity ~2.6.
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Physical properties
Pale blue-gray, translucent to semi-opaque, with a waxy to dull luster and irregular conchoidal fracture; Mohs hardness about 6.5–7, no cleavage, trigonal quartz structure, specific gravity ~2.6.
Formation & geological history
Forms when silica-rich groundwater fills cavities or replaces volcanic and sedimentary material; chalcedony commonly formed in the Cenozoic or older, depending on its host rock.
Uses & applications
Used for lapidary work, cabochons, carvings, and ornamental stone; this rough piece appears primarily a collecting specimen rather than gem-grade material.
Geological facts
The blue color may result from microscopic inclusions, scattering, or trace minerals; similar material can be mistaken for blue calcite, slag, or weathered glass.
Field identification & locations
Identify by its hardness, waxy appearance, lack of cleavage, and inability to scratch it with a steel knife; common in volcanic terrains, silica-rich gravels, and sedimentary chert beds.
