sedimentary

Yellow Chert (Chert / Cryptocrystalline Quartz)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Tan to yellowish-brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Tan to yellowish-brown
Luster: Waxy to dull

Identified June 2, 2026More sedimentary →

Explore Yellow Chert (Chert / Cryptocrystalline Quartz) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 (Mohs scale); Color: Tan to yellowish-brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or sponges) or chemical precipitation in marine environments. Often found as nodules within limestone or chalk beds.

Uses & applications

Historically used for making stone tools due to its sharp edges. Today used in construction aggregate, landscaping, and occasionally as a semi-precious gemstone (Jasper variant) for lapidary work.

Geological facts

Chert is so hard it can scratch glass and steel. It was one of the most important minerals for early humans to create arrowheads, scrapers, and fire-starting tools.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture and its ability to scratch a knife blade. Commonly found in riverbeds, glacial tills, and coastal areas.