sedimentary
Chert (Jasper variety)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: Brown, red, or greenish-brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific gravity: 2.5-2.8
- Hardness
- 6
- Color
- Brown, red, or greenish-brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, red, or greenish-brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific gravity: 2.5-2.8
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation from groundwater within sedimentary rock layers. It is often found in nodules or as bedded deposits.
Uses & applications
Historically used for stone tools (arrowheads). Modernly used in jewelry, lapidary art, and as a decorative stone in landscaping.
Geological facts
Chert was one of the first materials used by early humans for fire-starting and tool-making due to its sharp edges when broken. Jasper is a variety of chert colored by iron impurities.
Field identification & locations
Identify by its 'shell-like' conchoidal fracture and its ability to scratch glass. It is commonly found in stream beds or within limestone and dolomite formations.
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Cone-in-cone structure (Secondary Sedimentary Structure)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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