sedimentary

Iron-rich chert or silicified sedimentary rock

Microcrystalline quartz (SiO₂), likely ferruginous chert/jasper

AI-generated identification · may be incorrect

Typically Mohs 6.5–7, opaque tan-brown to reddish-brown with earthy iron-oxide staining, dull to waxy luster, and conchoidal fracture; crystals are microscopic and cleavage is absent. The specimen appears dense and fine-grained, though its exact identity cannot be confirmed from an image alone.

Identified August 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica replaces or cements sediment, commonly incorporating hematite or goethite that produces the orange-brown color. Such chert may range from Precambrian to younger sedimentary ages and occurs in nodules, beds, or weathered gravels.

Uses & applications

Used locally as a durable aggregate, road material, toolstone, and decorative stone; attractive pieces may be cut or polished as jasper. This hand specimen has modest commercial value.

Geological facts

Iron staining can create mottled patterns and mimic jasper. A sharp edge and glassy conchoidal break distinguish chert from softer clay-rich rocks.

Field identification & locations

Common in sedimentary terrains and stream gravels worldwide; test for hardness by whether it scratches ordinary glass, and inspect a fresh fracture for a smooth waxy surface. Estimated value: $2–$15 for a common specimen, or $20–$75 if unusually patterned and polished.