mineral

Polished blue chalcedony (likely seam agate)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent pale blue, cream, and brown with waxy to vitreous luster. Quartz fibers form a cryptocrystalline structure, with no visible cleavage and conchoidal fracture.

Identified August 15, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; translucent pale blue, cream, and brown with waxy to vitreous luster. Quartz fibers form a cryptocrystalline structure, with no visible cleavage and conchoidal fracture.

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, commonly during the Cenozoic or older volcanic episodes; iron oxides create the brown-red patches. The specimen has been cut or tumbled and polished.

Uses & applications

Used for cabochons, beads, carvings, and decorative objects; attractive pieces are popular with lapidary collectors. It is not generally used as a major construction stone.

Geological facts

Blue chalcedony gets its color from trace minerals, microscopic inclusions, or light-scattering effects rather than a separate blue mineral. The image may also represent blue lace agate or dyed chalcedony, which cannot be confirmed visually alone.

Field identification & locations

Identify by its waxy translucence, smooth curved fracture, lack of cleavage, and ability to scratch ordinary glass; a quartz-specific gravity is about 2.6. Common sources include Namibia, Turkey, Brazil, Madagascar, and the western United States.