sedimentary

Chert (Chalcedony-rich sedimentary rock)

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, beige, off-white; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6

Hardness: 7 on Mohs scale
Color: Tan, beige, off-white
Luster: Waxy to dull

Identified July 7, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, beige, off-white; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6

Formation & geological history

Formed primarily by the precipitation of silica in sedimentary environments, often within limestone or marl. It can originate from biological remains like diatom or radiolarian tests or through chemical replacement processes.

Uses & applications

Used historically for tool-making (arrowheads, scrapers) due to its sharp edges; used today as a construction aggregate and as a specimen for lapidary collectors.

Geological facts

Chert has been used by humans for hundreds of thousands of years to create fire (flint is a variety of chert) and sharp-edged tools. It is incredibly durable and resists chemical weathering.

Field identification & locations

Identify in the field by its distinct waxy appearance, extreme hardness (it will scratch glass/steel), and conchoidal (shell-like) fracture patterns. Found worldwide in sedimentary basins.