sedimentary

Chert (Yellow Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Yellow, tan, brownish-yellow; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 Mohs
Color: Yellow, tan, brownish-yellow
Luster: Waxy to dull

Identified July 1, 2026More sedimentary →

Explore Chert (Yellow Jasper) 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; Color: Yellow, tan, brownish-yellow; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed from the accumulation of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools (flintknapping) due to sharp edges; currently used for lapidary work, jewelry, and as a decorative landscaping stone.

Geological facts

Yellow jasper is a variety of chert that gets its color from iron oxide (goethite or limonite) inclusions. It has been used by humans for millions of years to create scrapers and arrowheads.

Field identification & locations

Identify in the field by its smooth, waxy surface and its ability to scratch glass. Look for curved, shell-like (conchoidal) fractures on broken edges. Common in riverbeds and sedimentary outcrops.