sedimentary
Chert (Pink and Yellow Chert)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Pink, yellow, white; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Pink, yellow, white
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, yellow, 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 silica-rich microfossils or inorganic silica precipitation in sedimentary environments. Common in marine limestone environments and as nodules or layered beds.
Uses & applications
Historically used for stone tools (arrowheads). Modernly used as landscaping rock, road base, and for decorative lapidary work or semi-precious jewelry.
Geological facts
Chert is essentially the same mineral as jasper or agate; it is often found in the US Midwest, particularly in Missouri and Illinois where it is known as Burlington Chert.
Field identification & locations
Identified by its extreme hardness (scratches glass), waxy feel, and smooth curved conchoidal fractures. High-quality pieces often glow when backlit.
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