sedimentary
Chert (Yellow Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs Scale); Color: Yellow, tan, mustard; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.65.
- Hardness
- 6
- Color
- Yellow, tan, mustard
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs Scale); Color: Yellow, tan, mustard; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.65.
Formation & geological history
Formed in marine or freshwater environments through the accumulation of silica-rich organic remains or chemical precipitation. This specific yellow color is typically caused by goethite or limonite inclusions.
Uses & applications
Historically used for stone tools (knapping) due to its sharp conchoidal fracture. Modernly used in jewelry making, lapidary arts as 'jasper', and as a collector specimen.
Geological facts
Chert and Jasper are essentially the same mineral, with Jasper being opaque and Chert being the broader geophysical term. Yellow Jasper is often associated with the solar plexus chakra in metaphysical beliefs and has been used for talismans for thousands of years.
Field identification & locations
Identified in the field by its hardness (will scratch glass), waxy feel, and sharp, shell-like (conchoidal) edges when broken. It is a very common material found globally in sedimentary rock layers and riverbeds.
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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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Shale or Slaty Mudstone
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