sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Red-brown to purple; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Red-brown to purple
Luster: Waxy to vitreous

Identified June 30, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Red-brown to purple; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Frequently found in marine deposits where silica nodules replace existing limestone or chalk.

Uses & applications

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

Geological facts

Chert has been used by humans for millions of years to create arrowheads and scrapers. The reddish-purple variety seen here is often classified as jasper if it is opaque and highly colored by iron inclusions.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its ability to scratch glass. Commonly found in riverbeds, glacial till, and embedded in limestone outcrops.