sedimentary

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and dark grey mottling. Luster: Dull to waxy. Crystal Structure: Hexagonal (microscopic). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Brown, tan, and dark grey mottling
Luster: Dull to waxy

Identified April 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from groundwater within sedimentary beds, typically in marine environments. Age ranges from Precambrian to Recent.

Uses & applications

Historically used for stone tools (arrowheads). Modernly used in jewelry (lapidary), as a road aggregate, and for landscaping.

Geological facts

Chert has a conchoidal fracture which creates sharp edges, making it the primary material for prehistoric tool making. It is often found as nodules inside limestone or chalk beds.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like fracture pattern. Common in riverbeds and limestone outcrops globally.