sedimentary

Chert (Yellow Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scaled); Color: Dull yellowish-brown to tan with darker dendritic or spotted inclusions; Luster: Waxy to dull; Crystal structure: Cryptocrystalline/Microcrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Luster: Waxy to dull

Identified June 18, 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

Formation & geological history

Formed via the accumulation of silica-rich microfossils (like radiolarians) or chemical precipitation in marine or groundwater environments. This specimen appears water-worn, likely from a river or beach setting.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges. Modern uses include tumbling for decorative 'river rocks,' lapidary work for jewelry, and as an industrial abrasive.

Geological facts

Yellow jasper is essentially a variety of chert colored by iron hydroxide impurities (like goethite). It was highly valued by early humans for making scrapers and arrowheads because of its predictable fracture pattern.

Field identification & locations

Identified in the field by its hardness (it will scratch glass), its smooth, waxy surface when wet, and its characteristic curved (conchoidal) breaks. Often found in riverbeds or landscaping gravel.