Chert (Jasper/Flint variety)

Physical Properties

Hardness: 7 (Mohs scale); Color: Brown, tan, reddish; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & Geological History

Formed through the accumulation of silica-rich microfossils or precipitation from silica-rich fluids within sedimentary rock layers, often occurring as nodules or beds.

Uses & Applications

Historically used for stone tools and weapons due to its sharp edges; currently used for decorative stone, landscaping, and lapidary art including cabochons.

Geological Facts

Chert is so hard it can scratch steel and was used by ancient humans to create sparks for fire-starting. Jasper is an opaque variety specifically valued for its aesthetic patterns.

Field Identification & Locations

Identify by its waxy appearance and shell-like (conchoidal) fracture pattern. Commonly found in limestone beds, riverbeds, and gravel deposits globally.

Identified on: 4/17/2026

Mode: Standard