sedimentary

Chert (varieties including Flint or Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, red, and grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Brown, tan, red, and grey
Luster: Waxy to dull

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, red, and grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & geological history

Forms in sedimentary rocks through the accumulation of siliceous remains of organisms (like diatoms or radiolaria) or via chemical precipitation from silica-rich groundwater replacing carbonate or wood.

Uses & applications

Historically used for stone tools and fire-starting; currently used for road surfacing, gravel, jewelry (as jasper), and as a collector's specimen.

Geological facts

Because it breaks with a conchoidal fracture creating sharp edges, it was the primary material for prehistoric arrowheads and knives. It is chemically very stable and resistant to weathering.

Field identification & locations

Identify in the field by its hardness (scratches glass), waxy appearance, and shell-like (conchoidal) fracture patterns. It is frequently found as nodules in limestone or as bedded deposits.