sedimentary

Iron-rich chert or jasper

Microcrystalline quartz (SiO₂), variably stained by iron oxides/hydroxides

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque gray, olive-brown, yellow, and rusty-red colors with dull to waxy luster. It is cryptocrystalline, lacks visible cleavage, and commonly breaks with a conchoidal fracture; the image alone cannot confirm the exact variety.

Identified August 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed when silica-rich fluids replaced or cemented sediment, with later iron staining producing the yellow-brown coloration. Such cherts commonly formed during Precambrian to younger sedimentary episodes in marine or volcanic environments.

Uses & applications

Used historically for sharp tools and fire-starting, and today for carvings, lapidary objects, landscaping, and inexpensive cabochons. Construction use is limited but crushed chert can serve as aggregate.

Geological facts

The compact microcrystalline quartz can produce exceptionally sharp edges when fractured. Its colors may come from limonite/goethite or hematite rather than metallic minerals.

Field identification & locations

Look for very high hardness, no cleavage, waxy surface, and conchoidal fracture; it should scratch ordinary glass. Common sources include sedimentary basins and volcanic terrains worldwide; a streak, specific gravity, and thin-section test would refine identification.