sedimentary

Chert (with Limestone/Marble traces)

Silicon Dioxide (SiO2) / Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Gray, tan, white with iron staining; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Gray, tan, white with iron staining
Luster: Waxy to dull

Identified June 5, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: Gray, tan, white with iron staining; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains (diatoms, radiolarians) or chemical precipitation in marine environments; age varies from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (flintknapping); currently used in road construction, landscape gravel, and as abrasive media.

Geological facts

Chert is so hard it can create sparks when struck against steel. It is one of the most durable rocks on the Earth's surface and often persists long after surrounding limestone has eroded.

Field identification & locations

Identify in the field by its hardness (it will scratch glass) and its sharp, shell-like (conchoidal) edges when broken. Common in riverbeds and limestone outcrops.