sedimentary
Chert with Quartz Vein
Microcrystalline Quartz (SiO2)
Hardness: 7 Mohs scale; Color: Grey, black, and white; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 Mohs scale
- Color
- Grey, black, and white
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 Mohs scale; Color: Grey, black, and white; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed from the accumulation of siliceous remains of marine organisms or via chemical precipitation of silica-rich fluids in limestone cavities. This specimen features a prominent white hydrothermal quartz vein cutting through the darker host chert.
Uses & applications
Historically used for stone tools (arrowheads). Modern uses include landscaping, construction aggregate, and as a collector's specimen.
Geological facts
Chert has been used by humans for millions of years because it breaks with sharp edges. This specific piece shows a secondary mineralization event where quartz filled a fracture in the older rock.
Field identification & locations
Identify in the field by its hardness (will scratch glass), conchoidal (shell-like) fracture, and smooth, waxy surface. Commonly found in riverbeds or within limestone and chalk deposits.
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