sedimentary
Chert (Jasper variety)
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and mustard yellow. Luster: Dull to waxy. Crystal structure: Trigonal (microscopic). Cleavage: None, exhibits conchoidal (shell-like) fracture. Specific gravity: 2.65.
- Hardness
- 6
- Color
- Brown, tan, and mustard yellow
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and mustard yellow. Luster: Dull to waxy. Crystal structure: Trigonal (microscopic). Cleavage: None, exhibits conchoidal (shell-like) fracture. Specific gravity: 2.65.
Formation & geological history
Forms through the accumulation of silica-rich organic remains or chemical precipitation from groundwater within limestone or slate beds. This specimen likely formed in a marine environment during various geological periods.
Uses & applications
Used historically for stone tools and arrowheads due to its sharp edges; used today as decorative stones, in lapidary work (polishing), and as a landscaping material.
Geological facts
Chert is so hard it can create sparks when struck against steel. It is one of the most common materials used by prehistoric humans for tool making.
Field identification & locations
Identify by its 'flint-like' waxy texture, smooth conchoidal fractures, and inability to be scratched by a steel knife. Commonly found in riverbeds or as nodules in limestone outcrops.
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