sedimentary
Chert (Red Jasper variant)
Silica (SiO2)
Hardness: 7 on Mohs scale. Color: Deep reddish-brown (hematite inclusions) with translucent gray/white core. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Deep reddish-brown (hematite inclusions) with translucent gray/white core. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich microfossils (radiolaria or diatoms) or chemical precipitation in marine environments. The red color suggests the presence of iron oxide during formation.
Uses & applications
Historically used for stone tools due to sharp edges; currently used for lapidary work, jewelry, landscaping, and as a collector's specimen.
Geological facts
Chert has been used by humans for millions of years to create arrowheads and scrapers. Red jasper is often considered a spiritual stone in various cultures, symbolizing grounding and strength.
Field identification & locations
Identify by its characteristic conchoidal (shell-like) fracture and high hardness (it will scratch glass). Commonly found in sedimentary basins or as nodules in limestone. Collectors look for smooth, waxy surfaces and vibrant colors.
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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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