sedimentary
Chert (Yellow Jasper variant)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7.0 (Mohs scale); Color: Yellow to tan with brown pits; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Yellow to tan with brown pits
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7.0 (Mohs scale); Color: Yellow to tan with brown pits; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich marine organisms or chemical precipitation from groundwater within sedimentary layers. This specific specimen suggests a river-tumbled pebble with pockmarks likely caused by chemical weathering or biological borings.
Uses & applications
Used historically for stone tools due to its sharp edges; used today as landscaping stone, lapidary material for tumbling, and in jewelry.
Geological facts
Chert is so durable it can survive millions of years of transport in rivers. Varieties like Jasper are valued by collectors for their unique patterns and high polish potential.
Field identification & locations
Identify in the field by its waxy texture and conchoidal (shell-like) fractures. It will easily scratch glass. Commonly found in riverbeds, gravel pits, and coastal areas.
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