sedimentary

Weathered chert or jasper nodule

Microcrystalline quartz (SiO₂), likely chalcedony/jasper with iron-oxide staining

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; tan, amber-brown, and rusty red coloration; dull to waxy luster with a locally smoother, possibly translucent surface. Massive, fine-grained, noncleavable, and typically conchoidally fracturing; the rough coating appears weathered or encrusted.

Identified August 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or fills cavities in sedimentary rock, later weathering free as a rounded nodule or cobble. Its exact geological age cannot be determined from the image; chert and jasper occur from Precambrian to modern deposits.

Uses & applications

Used for ornamental carvings, cabochons, beads, and lapidary work; historically, chert was valuable for producing sharp tools and fire sparks. Common pieces have modest collecting value.

Geological facts

The amber area may be translucent chalcedony, while the opaque rusty material is likely iron-stained jasper or weathered rind. A precise identification requires a fresh edge, hardness testing, and ideally a specific-gravity or microscope examination.

Field identification & locations

Common in gravel beds, desert pavements, volcanic terrains, and sedimentary formations worldwide, especially where silica-rich fluids circulated. It should scratch ordinary glass, resist a steel knife, and show a smooth waxy or glassy fracture when freshly broken.