sedimentary

Chert / Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Dark grey to black with orange/brown iron staining and white veins; Luster: Dull to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Luster: Dull to waxy

Identified May 30, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as chemical precipitates from silica-rich fluids or from the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) in marine environments.

Uses & applications

Primarily used as a lapidary material for polishing and jewelry. Historically used for making stone tools (arrowheads, scrapers) due to its sharp edges.

Geological facts

This specimen appears to be water-worn, likely found in a riverbed or on a beach. The white veins are typically quartz or calcite filling fractures in the host rock.

Field identification & locations

Identify in the field by its hardness (will scratch glass), conchoidal (shell-like) fracture, and smooth texture. Common in sedimentary basins worldwide.