sedimentary
Chert (Jasper variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs), Color: Dark greenish-blue to brownish, Luster: Waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Dark greenish-blue to brownish, Luster: Waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the accumulation of silica-rich organic remains or chemical precipitation in marine environments; age varies from Precambrian to Cenozoic.
Uses & applications
Used historically for stone tools, currently for lapidary work, jewelry (cabochons), and as a collector's specimen.
Geological facts
This specimen appears to be a variety of chert or jasper, which are microcrystalline forms of silica that break with sharp edges, making them the primary material for prehistoric arrowheads.
Field identification & locations
Identify by its waxy texture, great hardness (scratches glass), and distinctive shell-like (conchoidal) fracture pattern. Found globally in sedimentary beds.
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