Chert (Jasper variety)

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Variegated brown, tan, and grey/green; Luster: Waxy to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65

Formation & Geological History

Formed through the accumulation of silica-rich fluids in sedimentary environments or the replacement of organic/calcite materials. This specimen appears as a river-worn or water-smoothed nodule, common in various geological ages.

Uses & Applications

Historically used for making stone tools (arrowheads/scrapers); currently used for lapidary work, jewelry (cabochons), and as a decorative stone in landscaping.

Geological Facts

Chert is so hard it can strike sparks against steel, making it a primary fire-starting tool for ancient civilizations. It is a dense, opaque variety of chalcedony.

Field Identification & Locations

Identify by its extreme hardness (will scratch glass), waxy feel when polished, and distinctive shell-like (conchoidal) fracture pattern. Commonly found in stream beds or gravel pits.

Identified on: 4/15/2026

Mode: Standard