sedimentary
Chert (Jasper variety)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, earthy tones (likely due to iron oxide impurities); Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, earthy tones (likely due to iron oxide impurities); Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specific specimen appears to be a water-worn river pebble or glacial till component, possibly millions of years old based on local stratigraphy.
Uses & applications
Historically used for stone tools (flintknapping); currently used as an abrasive, in landscaping aggregate, and as a semi-precious gemstone for decorative carvings and jewelry when highly polished.
Geological facts
Chert and its variety Jasper were among the first resources used by early humans to create sharp cutting tools and fire-starting kits because of their conchoidal fracturing patterns and sparked when struck with steel.
Field identification & locations
Identify in the field by its hardness (it can scratch glass), its smooth 'waxy' texture when broken, and the lack of visible grains. Common in gravel beds, riverbanks, and limestone outcrops globally. Collectors look for unique banding or patterns.
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