sedimentary
Chert (Yellow Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Yellow to brownish-yellow due to iron oxides, Luster: Waxy to dull, Crystal structure: Trigonal/Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Yellow to brownish-yellow due to iron oxides, Luster: Waxy to dull, Crystal structure: Trigonal/Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed via the precipitation of silica-rich fluids within sedimentary rock layers or through the accumulation of siliceous organisms like radiolaria. Yellow varieties often derive their color from goethite or limonite inclusions.
Uses & applications
Used historically for stone tools due to sharp edges; commonly used today for lapidary work, jewelry (cabochons), and landscaping gravel.
Geological facts
Yellow jasper is often associated with the solar plexus chakra in metaphysical circles. Historically, chert was a primary material for arrowheads and spear points because of its predictable fracturing patterns.
Field identification & locations
Identify in the field by its smooth, waxy surface and conchoidal (shell-like) fractures. It will typically scratch glass but cannot be scratched by a steel nail. Commonly found in river beds or as nodules in limestone.
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