Chert (Grey-Green Var.)

Hardness: 7 (Mohs scale); Color: Dull grey to light green; Luster: Dull or waxy; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formed by the precipitation of silica-rich fluids within sedimentary environments, often replacing carbonate materials. This specimen likely originates from marine deposits where silica from organic sources like diatoms or radiolarians accumulated. It can range from hundreds of millions to billions of years old.

Used historically for stone tools and weapons due to its sharp edges. Today, it is used in road construction as an aggregate, in landscaping, and occasionally as a low-cost tumble stone for jewelry or as a starting material for fire-making kits (flint-and-steel).

Chert is a chemical sedimentary rock and is one of the most durable materials on Earth. It is a cousin to flint, jasper, and agate. In prehistoric times, it was the 'high technology' of the era because it could be knapped into razor-sharp cutting tools.

Identify in the field by its extreme hardness (cannot be scratched by steel) and smooth, shell-like (conchoidal) fracture pattern. Commonly found in limestone and dolomite beds as nodules or layers. Known locations include the Midwestern US and Southern UK.