sedimentary
Chert (Jasper)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 Mohs, Color: reddish-brown/tan, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65
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Physical properties
Hardness: 7 Mohs, Color: reddish-brown/tan, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation from groundwater within sedimentary beds. These specimens are often found as nodules or pebbles in stream beds or coastal deposits.
Uses & applications
Used historically for stone tools due to sharp fracture edges; currently used for decorative gravel, lapidary tumbling, and jewelry.
Geological facts
Chert has been used by humans for hundreds of thousands of years to create arrowheads and scrapers. Red varieties are specifically known as Jasper.
Field identification & locations
Identify by its conchoidal (shell-like) fracture pattern and its ability to scratch glass. It is common in riverbeds and limestone formations worldwide.
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