sedimentary

Chert (often called Jasper or Flint)

Microcrystalline Silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale). Color: Brownish-red to earthy tan. Luster: Dull to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Brownish-red to earthy tan
Luster: Dull to waxy

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale). Color: Brownish-red to earthy tan. Luster: Dull to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or the chemical replacement of limestone/dolomite. Often found in nodules or bedded layers.

Uses & applications

Used historically for stone tools and arrowheads due to its sharp edges; modern uses include road surfacing and as a gemstone when colorful (Jasper).

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture produces edges sharper than a steel scalpel. It is highly resistant to chemical weathering.

Field identification & locations

Identify by its hardness (will scratch glass), smooth waxy feel on broken surfaces, and lack of visible grains. Commonly found in stream beds or limestone outcrops.