sedimentary
Chert (specifically Jasper/Flint)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, reddish-brown; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Brown, tan, reddish-brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, reddish-brown; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation from groundwater within sedimentary rock layers, predominantly during various geological eras from the Precambrian to Cenezoic.
Uses & applications
Historically used for stone tools and weapons (arrowheads); currently used in jewelry (as jasper), industrial abrasives, and as decorative landscaping stone.
Geological facts
Chert has been essential to human development as it was the primary material for the Stone Age tool industry due to its predictable conchoidal fracturing which produces sharp edges.
Field identification & locations
Identify in the field by its smooth, glass-like fracture surfaces, extreme hardness (it will scratch steel), and waxy feel. Commonly found in limestone or chalk deposits as nodules or layered beds.
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