mineral

Brecciated agate/chalcedony

Microcrystalline quartz (SiO₂), chiefly chalcedony with possible quartz and iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; gray, mauve, cream, and rusty-brown colors with translucent, waxy to dull luster. Irregular brecciated fragments and silica-filled fractures are visible; quartz has no cleavage and conchoidal fracture.

Identified August 10, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rock, depositing chalcedony and later quartz; brecciation indicates repeated fracturing and sealing. Usually Cenozoic to older, depending on the host volcanic terrain.

Uses & applications

Used for cabochons, tumbled stones, carvings, lapidary slabs, and ornamental objects; too small or irregular for most architectural uses.

Geological facts

The mosaic texture reflects broken rock fragments cemented by silica, while iron oxides create the orange-brown staining. It may also be marketed as brecciated jasper if it is mostly opaque.

Field identification & locations

Identify by its very hard, glass-like fracture, waxy silica texture, and contrasting angular patches; it commonly occurs in volcanic terrains and agate gravels. Exact identification requires testing hardness, translucency, and acid response.