sedimentary
Chert (Yellow Jasper)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: Yellowish-brown (due to iron oxides); Luster: Dull to waxy; Crystal Structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Yellowish-brown (due to iron oxides)
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Yellowish-brown (due to iron oxides); Luster: Dull to waxy; Crystal Structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) or inorganic precipitation from silica-rich fluids. It occurs as nodules or bedded deposits within limestone or dolomite. Geological age varies from Precambrian to modern.
Uses & applications
Historically used for stone tools/weaponry (arrowheads) due to sharp edges; currently used in lapidary work, jewelry (cabochons), landscaping, and as an abrasive in some industrial processes.
Geological facts
Jasper is an opaque variety of chert. The yellow coloring is specifically known as 'Yellow Jasper' or 'Mookite' depending on the locality. It has been used by humans for over a million years for tool-making.
Field identification & locations
Identify in the field by its characteristic smooth, shell-like (conchoidal) fracture and its ability to scratch glass. It is commonly found in stream beds, gravel pits, and within sedimentary rock outcrops globally. Collectors should look for its smooth texture compared to surrounding rocks.
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