sedimentary

Chert (specifically Flint or Gray Chert)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray, tan, or smoky blue-gray; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Gray, tan, or smoky blue-gray
Luster: Waxy to dull

Identified February 5, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray, tan, or smoky blue-gray; 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 (like diatoms or radiolarians) or chemical precipitation from groundwater within limestone or chalk beds. Most specimens date from the Paleozoic to Mesozoic eras.

Uses & applications

Abrasives, construction aggregate, historical tool-making (arrowheads, scrapers), and landscaping. Occasionally used in jewelry as cabochons.

Geological facts

This specimen appears to be a 'lithic flake' or a crude biface tool, showing signs of 'knapping' (deliberate human shaping). Chert was the primary material for stone-age technology due to its ability to produce razor-sharp edges.

Field identification & locations

Identify in the field by its smooth, waxy surface and conchoidal (shell-like) fractures. It is commonly found in limestone outcrops, riverbeds, and as nodules in chalk. Collectors look for bulbs of percussion or ripple marks indicating human modification.