sedimentary

Chert / Jasper

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs); Color: Pale green with brownish-yellow iron staining; Luster: Waxy to dull; Crystal structure: Trigonal (Microcrystalline); Cleavage: None (Conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Pale green with brownish-yellow iron staining
Luster: Waxy to dull

Identified July 9, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich fluids or biological remains (like radiolaria or diatoms) in sedimentary environments, later turning into solid rock through diagenesis. Frequently found as nodules in limestone or as bedded deposits.

Uses & applications

Historically used for making stone tools (arrowheads/scrapers) due to its sharp edges; today used for lapidary work, tumbling, and as a decorative landscape stone.

Geological facts

This specimen shows the characteristic waxy luster and smooth, rounded edges of water-worn river chert. The green color is often caused by the inclusion of chlorite or celadonite minerals during formation.

Field identification & locations

Identify in the field by its hardness (will scratch glass), waxy feel, and smooth shell-like (conchoidal) fractures. Found worldwide in creek beds and sedimentary rock formations, especially in the American Midwest and South.