sedimentary
Chert Nodule
Chert / Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7, Color: Brown, tan, with lighter inclusions, Luster: Dull to waxy (appears glossy when wet), Crystal structure: Cryptocrystalline
- Hardness
- 6
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Physical properties
Hardness: 6.5-7, Color: Brown, tan, with lighter inclusions, Luster: Dull to waxy (appears glossy when wet), Crystal structure: Cryptocrystalline
Formation & geological history
Formed as chemical or biochemical precipitate in sedimentary rock layers, often limestone or chalk. Rounded shape indicates it was tumbled in a river or beach environment.
Uses & applications
Commonly collected by rockhounds, historically used for making stone tools (flintknapping) due to conchoidal fracture.
Geological facts
Chert nodules are often harder than the surrounding sedimentary rock, so they weather out and accumulate in riverbeds or beaches.
Field identification & locations
Identify by its hardness (scratches glass), smooth but dull surface (unless polished or wet), and conchoidal fracture if broken. Often found in gravel beds or beaches.
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