Chert (specifically Jasper/Carnelian variety)

Physical Properties

Hardness: 6.5-7 (Mohs scale). Color: Orange-red, tan, and translucent white. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Formation & Geological History

Formed through the accumulation of silica-rich microfossils or precipitation from silica-rich hydrothermal fluids. This specimen shows typical sedimentary fracturing and iron-oxide staining which gives it the reddish-orange hue.

Uses & Applications

Historically used for stone tools (knapping). Currently used as decorative stones, in lapidary work (jewelry and cabochons), and as landscaping gravel.

Geological Facts

Chert was one of the most important minerals for early humans because its conchoidal fracture creates extremely sharp edges for hunting and processing food.

Field Identification & Locations

Identify in the field by its waxy texture, inability to be scratched by a steel knife, and smooth, shell-like (conchoidal) breaks. It is commonly found in riverbeds and limestone formations worldwide.

Identified on: 4/13/2026

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