mineral
Chert or chalcedony fragment
Microcrystalline quartz (SiO₂), likely ferruginous chalcedony/jasper
AI-generated identification · may be incorrectHardness 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.
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Physical properties
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.
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.
