sedimentary
Yellow Chert (Jasper)
Chalcedony (SiO2) with iron oxide inclusions
Hardness: 6.5-7 on Mohs scale; Color: mustard yellow to tan; Luster: waxy to dull; Crystal structure: cryptocrystalline; Cleavage: none, exhibits conchoidal fracture; Specific gravity: approx 2.6
- Hardness
- 6
- Color
- mustard yellow to tan
- Luster
- waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: mustard yellow to tan; Luster: waxy to dull; Crystal structure: cryptocrystalline; Cleavage: none, exhibits conchoidal fracture; Specific gravity: approx 2.6
Formation & geological history
Formed from the precipitation of silica-rich fluids in sedimentary environments or through the replacement of limestone. This specimen likely originates from Paleozoic to Mesozoic era deposits.
Uses & applications
Historically used for stone tools and arrowheads; currently used in jewelry (cabochons), as landscaping stone, and for specimen collecting.
Geological facts
Chert and Jasper are often used interchangeably when the color is opaque; the yellow tint is specifically caused by the presence of goethite or limonite. It is one of the most durable sedimentary rocks.
Field identification & locations
Identify in the field by its smooth, waxy feel and the way it breaks into curved, glass-like shards (conchoidal fracture). Frequently found in riverbeds, gravel pits, and eroding out of limestone outcrops.
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