sedimentary

Yellow Chert

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Yellow-brown, tan, or ochre; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Yellow-brown, tan, or ochre
Luster: Waxy to dull

Identified June 27, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Yellow-brown, tan, or ochre; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed by the accumulation of siliceous remains or through the chemical precipitation of silica in sedimentary environments such as marine basins. It is often found as nodules or layers within limestone and chalk.

Uses & applications

Historically used for making stone tools due to its sharp edges; used today as a decorative stone, in construction aggregate, and occasionally in lapidary work.

Geological facts

Chert is virtually indestructible and can survive millions of years of weathering. Yellow variants are often colored by iron oxides like goethite or limonite.

Field identification & locations

Identify by its waxy luster, conchoidal (shell-like) fracture, and inability to be scratched by a steel knife. Commonly found in riverbeds and limestone outcrops globally.