sedimentary
Chert (potentially Jasper or Agatized Chert)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Reddish-brown with white/opaque quartz veins. Luster: Waxy to vitreous. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Reddish-brown with white/opaque quartz veins
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Reddish-brown with white/opaque quartz veins. Luster: Waxy to vitreous. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture).
Formation & geological history
Formed via the accumulation of siliceous remains of organisms (like diatoms or radiolaria) or through chemical precipitation from silica-rich fluids in limestone/chalk or volcanic host rocks. Often found in Phanerozoic age strata.
Uses & applications
Historically used for stone tools (flintknapping). Modern uses include decorative landscaping, jewelry (when polished), and as a minor abrasive.
Geological facts
Chert is so hard it can strike sparks against steel. The reddish color in this specimen is likely due to iron oxide impurities (Hematite).
Field identification & locations
Identify by its characteristic conchoidal (shell-like) fracture and the ability to scratch glass. Commonly found in stream beds or as nodules within limestone or volcanic formations.
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