mineral

Brown chalcedony (agate-like flint/chert fragment)

Chalcedony, microcrystalline quartz (SiO₂); identification is tentative from the photo

AI-generated identification · may be incorrect

Translucent tan, cream, and brown with a waxy-to-dull luster and irregular, sharp fracture; quartz hardness is about 7 Mohs, with no cleavage. Crystal structure is microscopic trigonal quartz fibers.

Identified October 4, 2026More mineral →

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Physical properties

Translucent tan, cream, and brown with a waxy-to-dull luster and irregular, sharp fracture; quartz hardness is about 7 Mohs, with no cleavage. Crystal structure is microscopic trigonal quartz fibers.

Formation & geological history

Silica-rich water deposits quartz in cavities or replaces sediment, forming chalcedony; such material occurs across a wide range of geological ages.

Uses & applications

Commonly cut or polished for beads, cabochons, and decorative objects; rough fragments are collected or used as lapidary material.

Geological facts

Chalcedony is a broad term for microcrystalline quartz; banded varieties are called agate, while opaque varieties may be called jasper.

Field identification & locations

Look for a waxy surface, translucence at thin edges, and conchoidal (curved-shell) fracture; distinguish it from glass by its hardness and lack of bubbles. Found worldwide in volcanic rocks and sedimentary deposits.