sedimentary

Chert

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 Mohs; Color: Tan, cream, and grey mottled; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6

Hardness: 6
Color: Tan, cream, and grey mottled
Luster: Waxy to dull

Identified June 17, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Tan, cream, and grey mottled; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6

Formation & geological history

Formed in marine environments through the accumulation of silica-rich organisms (like diatoms or radiolaria) or through chemical precipitation in sedimentary rock layers. This specimen shows signs of fluvial tumbling (water rounding).

Uses & applications

Historically used for stone tools (arrowheads, scrapers) due to its sharp edges when broken. Currently used in road gravel, as decorative landscaping stone, and for flint-knapping enthusiasts.

Geological facts

Chert is essentially the same material as flint; however, 'flint' is often specifically used for chert found in chalk or marly limestone. It is one of the most common materials found in prehistoric archaeological sites.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its waxy texture, and its smooth, curved conchoidal fractures. Commonly found in river beds and sedimentary outcrops globally.