sedimentary

Chert (specifically Flint or Common Opal variant)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Cream, tan, and light gray with iron staining; Lustre: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Cream, tan, and light gray with iron staining

Identified March 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) or through the chemical precipitation of silica in limestone or chalk beds. Most specimens date from the Phanerozoic eon.

Uses & applications

Historically used for stone tools (arrowheads/knives) due to sharp edges; currently used for road surfacing, jewelry (as jasper or agate variants), and as a high-silica industrial resource.

Geological facts

Because of its conchoidal fracture, it breaks into pieces with edges sharper than a steel scalpel. It was the primary 'technological' material for humanity for over two million years.

Field identification & locations

Identify by its 'shell-like' curved fractures and its ability to scratch glass. It is commonly found as nodules in limestone or as bedded deposits in marine sedimentary layers.