sedimentary
Chert (Red Jasper variant)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: reddish-brown; Luster: waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.6-2.7.
- Hardness
- 6
- Color
- reddish-brown
- Luster
- waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: reddish-brown; 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 sedimentary basins. Often associated with rhythmic bedding in deep-sea deposits or as nodules in limestone.
Uses & applications
Historically used for stone tools and weapons due to its sharp edges; modernly used as a semi-precious gemstone in jewelry, for lapidary work, and as flux in metallurgy.
Geological facts
Red colors in chert are usually caused by iron oxide (hematite) inclusions. It was one of the primary materials used by prehistoric humans for knapping arrowheads and scrapers.
Field identification & locations
Identify by its smooth, waxy texture and conchoidal (shell-like) fracture patterns. Look for it in riverbeds, gravel deposits, or eroding out of sedimentary rock faces.
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