sedimentary
Chert (Jasper variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs). Color: Reddish-brown, tan, or orange-pink. Luster: Waxy to dull. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6 – 2.9.
- Hardness
- 6
- Color
- Reddish-brown, tan, or orange-pink
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs). Color: Reddish-brown, tan, or orange-pink. Luster: Waxy to dull. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6 – 2.9.
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids in sedimentary environments. Common in marine deposits and can vary in age from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools (knapping) due to its sharp edges. Modernly used for lapidary work, jewelry, and as decorative stone in gardens.
Geological facts
Jasper is an opaque variety of chalcedony. The reddish hues are typically caused by iron oxide (hematite) inclusions within the silica structure.
Field identification & locations
Identify in the field by its smooth, shell-like (conchoidal) fracture and its ability to scratch glass. It is commonly found in stream beds, beaches, and sedimentary basins worldwide.
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