sedimentary

Chert (Jasper/Agate variety)

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: tan, white, and brownish, Luster: waxy to vitreous, Crystal Structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Hardness: 6

Identified June 20, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: tan, white, and brownish, Luster: waxy to vitreous, Crystal Structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids within sedimentary environments. This specimen shows significant rounding from water erosion (alluvial/beach transport).

Uses & applications

Used historically for stone tools due to its sharp fracture; currently used for landscaping, as semi-precious gemstones when polished, and for geological study.

Geological facts

Chert is so durable that it often survives long after the surrounding rock has weathered away. The brownish patterns in this specimen are likely caused by iron oxide impurities.

Field identification & locations

Identify by its waxy texture, inability to be scratched by a steel knife, and smooth, curved (conchoidal) fracture surfaces. Commonly found in riverbeds and on beaches worldwide.