sedimentary

River-worn Chert

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs). Color: Pale olive green to tan with darker veining. Luster: Waxy to dull. Structure: Microcrystalline with conchoidal fracture patterns. Cleavage: None.

Hardness: 6
Color: Pale olive green to tan with darker veining
Luster: Waxy to dull

Identified July 7, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs). Color: Pale olive green to tan with darker veining. Luster: Waxy to dull. Structure: Microcrystalline with conchoidal fracture patterns. Cleavage: None.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. This specimen shows significant rounding and smoothing from fluvial (river) erosion.

Uses & applications

Historically used for stone tools and arrowheads; currently used for decorative garden stones, river rock landscaping, and as a material for rock tumbling.

Geological facts

Chert is so hard it can create sparks when struck against steel. Its microcrystalline structure allows it to break with very sharp edges, which is why it was prized by prehistoric humans for blades.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife), its waxy feel, and its smooth, rounded surface if found near water. Common in limestone regions and riverbeds.