sedimentary

Chert / Microcrystalline Quartz

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Tan, beige, brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Tan, beige, brown
Luster: Waxy to dull

Identified July 12, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: Tan, beige, brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of siliceous remains of marine organisms or the precipitation of silica from groundwater within sedimentary layers. This process can occur in various geological ages ranging from the Archean to the Cenozoic.

Uses & applications

Historically used for stone tools (flintknapping) due to its sharp edges when broken. Modern uses include road surfacing, decorative gravel, and as a raw material for silicon production.

Geological facts

Chert was one of the first minerals used by early humans to create arrowheads, scrapers, and axes. Flint is a specific dark variety of chert often found in chalk or limestone.

Field identification & locations

Identify in the field by its waxy luster and conchoidal (shell-like) fracture pattern. It will scratch glass easily. Commonly found in riverbeds, limestone outcrops, and coastal areas.