mineral

Chalcedony (likely agate/chert variety)

Microcrystalline quartz, SiO₂

AI-generated identification · may be incorrect

Translucent brown-gray material with waxy luster, conchoidal fracture, and subtle fibrous/banded texture. Hardness about 6.5–7 Mohs; no cleavage; specific gravity approximately 2.58–2.64.

Identified August 10, 2026More mineral →

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Physical properties

Translucent brown-gray material with waxy luster, conchoidal fracture, and subtle fibrous/banded texture. Hardness about 6.5–7 Mohs; no cleavage; specific gravity approximately 2.58–2.64.

Formation & geological history

Forms when silica-rich groundwater fills cavities or fractures, commonly in volcanic rocks, or replaces sediment. The image cannot establish a geological age; regional specimens may derive from Miocene volcanic-associated deposits or transported gravels.

Uses & applications

Used for cabochons, carvings, ornamental objects, abrasives, and lapidary collecting. This irregular piece has modest commercial value.

Geological facts

The curved, shell-like fracture and translucency strongly support chalcedony rather than ordinary glass. Brown coloration may reflect iron oxides or other inclusions; it could also be a weathered agate or chert fragment.

Field identification & locations

Commonly found in gravel, weathered volcanic terrain, and sedimentary deposits. Inspect for repeated curved bands, a waxy surface, and lack of visible large crystals; it should scratch ordinary glass but not quartz. Near 47.6°N, 19.3°E, transported chalcedony/chert in river or construction gravel is plausible.