mineral

Chert or chalcedony fragment

Microcrystalline quartz (SiO₂), likely ferruginous chalcedony/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; tan, reddish-brown, and whitish coloration with a dull to waxy luster and conchoidal-looking fracture. It appears massive rather than visibly crystalline, with no obvious cleavage; specific gravity is about 2.6.

Identified September 6, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities or replaces sediment, commonly in volcanic or sedimentary settings; iron staining produces the red-brown color. The specimen’s exact geological age cannot be determined from the image.

Uses & applications

Used for flaked stone tools, abrasives, carvings, cabochons, and decorative stone; attractive patterned pieces may be collected or polished.

Geological facts

Chert and chalcedony are varieties of microcrystalline quartz, and their fine texture allows sharp fractures suitable for prehistoric tools.

Field identification & locations

Identify it by its glassy/waxy appearance, very high hardness, lack of cleavage, and inability to scratch it with a steel knife; quartz should scratch glass. Common worldwide, especially in limestone beds, volcanic areas, and gravel deposits.