mineral

Blue-gray chalcedony (likely common quartz/chert)

Microcrystalline quartz, SiO₂; possibly weathered chert or chalcedony

AI-generated identification · may be incorrect

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.

Identified August 22, 2026More mineral →

Explore Blue-gray chalcedony (likely common quartz/chert) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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.