sedimentary

Chert (and Chalcedony)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7.0 (Mohs); Color: Gray, tan, or white with waxy luster; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7
Color: Gray, tan, or white with waxy luster

Identified June 2, 2026More sedimentary →

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Physical properties

Hardness: 7.0 (Mohs); Color: Gray, tan, or white with waxy luster; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary basins. Often occurs as nodules in limestone or bedded deposits.

Uses & applications

Historically used for stone tools and arrowheads; used industrially as a silica source, in construction aggregate, and occasionally in lapidary work.

Geological facts

Chert has a conchoidal fracture which means it breaks into very sharp edges, similar to glass, making it the primary material for prehistoric survival tools.

Field identification & locations

Identify by its waxy texture and ability to scratch glass. Commonly found in limestone outcrops, river beds, and glacial till. Collectors look for unique banding or vugs.