Grey and White Chert (Flint)

Hardness: 7 (Mohs scale), Color: Banded grey and white/cream, Luster: Waxy to vitreous, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formed through the precipitation of silica from groundwater or the accumulation of silica-rich organic remains (like diatoms or radiolarians) in marine environments. These specimens likely originated in limestone or chalk beds during various geological periods, most commonly from the Paleozoic to Mesozoic eras.

Historically used for stone tools (arrowheads, scrapers) and as a spark-generator for flintlock firearms. Modern uses include abrasives, road construction aggregate, and occasionally as decorative landscaping stone or tumbled pocket stones.

Chert is so hard it can scratch steel. When broken, it produces ultra-sharp edges that are still used today in specialized surgical scalpels because they are finer than even high-grade stainless steel.

Identify by its 'conchoidal' fracture (smooth, curved breaks like glass) and the fact that it cannot be scratched by a steel knife. It is commonly found in riverbeds, glacial tills, and as nodules within limestone outcrops. Collectors look for unique banding or 'picture' patterns.