sedimentary

Chert (Jasper-bearing)

Silicon dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Variegated black, brown, and reddish-orange, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified May 30, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: Variegated black, brown, and reddish-orange, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & geological history

Formed from the accumulation of silica-rich organic remains such as radiolaria or diatoms in deep marine environments. The iron content produces the reddish jasper-like hues. These rocks are often related to ancient seafloor deposits and can range from hundreds of millions of years in age.

Uses & applications

Historical use for sharp tools and weapons (flint-knapping); modern use includes landscaping, jewelry (when polished), and as a collection specimen.

Geological facts

Chert is so hard it can strike sparks from steel. Because of its dense, cryptocrystalline structure, it breaks with a circular 'conchoidal' fracture, similar to glass. This specimen shows significant weathering and staining from iron and manganese.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), waxy feel, and smooth curved fractures. Found globally, especially in coastal areas like the Pacific Northwest or in limestone beds.