sedimentary

Chert (specifically Yellow Jasper/Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Yellow, white, and grey; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Yellow, white, and grey
Luster: Waxy to vitreous

Identified May 20, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Yellow, white, and grey; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by chemical precipitation in marine or groundwater environments. It typically occurs as nodules or layers in limestone or chalk beds.

Uses & applications

Historically used for making stone tools (arrowheads). Today used in jewelry as lapidary material, in landscaping, and as a low-cost gemstone for collectors.

Geological facts

Yellow chert gets its color from iron oxide (limonite) impurities. Because of its hardness and conchoidal fracture, it can create sharp edges when struck, a process known as flintknapping.

Field identification & locations

Identify in the field by its smooth, waxy feel and the way it breaks into curved, shell-like patterns (conchoidal fracture). It will not be scratched by a steel pocketknife. Commonly found in riverbeds and areas with exposed sedimentary rock.