sedimentary

Chert (specifically var. Flint or Jasper-rich Breccia)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Gray, tan, and reddish-pink patches in this specimen; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Gray, tan, and reddish-pink patches in this specimen
Luster: Waxy to dull

Identified March 26, 2026More sedimentary →

Explore Chert (specifically var. Flint or Jasper-rich Breccia) in the encyclopedia →

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Physical properties

Formation & geological history

Formed through the precipitation of silica from groundwater or as a biochemical sediment on the ocean floor, filling voids in limestone or replacing carbonates. This specific specimen appears brecciated, likely formed in a high-pressure fault zone or collapse structure.

Uses & applications

Historically used for stone tools and weapons due to sharp edges; currently used for road surfacing, grinding media in industry, and occasionally as semi-precious gemstones (jasper).

Geological facts

Chert is so hard it can strike sparks from steel, a property that led to its use in flintlock firearms. It is incredibly durable and can survive millions of years of erosion.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and its curved, glass-like 'conchoidal' fracture patterns. Common in limestone regions and creek beds.