sedimentary

Chert

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Tan, brown, or earthy; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Tan, brown, or earthy
Luster: Dull to waxy

Identified June 25, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, brown, or earthy; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed by the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen appears weathered and possibly worked by heat or physical force.

Uses & applications

Historically used for making stone tools (lithics) like arrowheads and scrapers; currently used in construction aggregate and as a collector's specimen.

Geological facts

Chert is known for its incredible durability and its ability to fracture into extremely sharp edges, which made it the primary material for prehistoric technology for millions of years.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by steel) and its characteristic shell-like (conchoidal) fracture edges. Commonly found in limestone or chalk deposits.