sedimentary
Chert (Jasper/Chalcedony)
Microcrystalline Silica (SiO2)
Hardness: 6.5-7; Color: Reddish-tan to pinkish-brown (due to iron oxides); Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Reddish-tan to pinkish-brown (due to iron oxides)
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7; Color: Reddish-tan to pinkish-brown (due to iron oxides); Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline; 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 volcanic environments. Often found as nodules or layers in limestone/dolomite beds.
Uses & applications
Historically used for making stone tools (arrowheads/scrapers) due to conchoidal fracturing. Modern uses include abrasives, gemstones (when colorful), and landscaping.
Geological facts
This specimen appears to be a 'flake' or debitage, possibly a waste piece from historical tool making. Its chemical composition is identical to quartz, but its microscopic structure makes it much tougher and less brittle.
Field identification & locations
Identify by its waxy appearance, translucency at thin edges, and sharp, shell-like (conchoidal) fracture surfaces. Commonly found in riverbeds and limestone outcrops.
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