sedimentary
Chert (specifically Yellow Jasper)
Sedimentary Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Yellow, tan, or mustard-brown due to iron oxide inclusions; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
- Hardness
- 6
- Color
- Yellow, tan, or mustard-brown due to iron oxide inclusions
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Yellow, tan, or mustard-brown due to iron oxide inclusions; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by the chemical precipitation of silica in groundwater. This specimen appears water-worn, likely from a river or beach environment, and can range from 10 million to over 2 billion years old depending on the local geology.
Uses & applications
Historically used for stone tools and arrowheads due to its sharp edges; currently used for lapidary work (cabochons), river rock landscaping, and as a collector's specimen.
Geological facts
Chert and Jasper are among the oldest materials used by early humans for hunting and fire-starting. The yellow color specifically indicates the presence of goethite or limonite (iron hydroxides).
Field identification & locations
Identify in the field by its smooth, waxy texture and shell-like (conchoidal) fractures. It will easily scratch glass. Commonly found in riverbeds, limestone outcrops, and coastal beaches.
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