sedimentary
Banded Jasper / Chert
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Red, brown, yellow, tan; Luster: Dull to waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Red, brown, yellow, tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Red, brown, yellow, tan; Luster: Dull to waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation in ancient marine or hydrothermal environments. Iron oxides produce the red and brown coloration. These deposits can range from Precambrian to Cenozoic in age.
Uses & applications
Used for lapidary work, cabochons for jewelry, garden landscaping, and as decorative display specimens for collectors.
Geological facts
The concentric and wavy bands are often referred to as 'picture jasper' if they resemble landscapes. Jasper has been used by humans for thousands of years to create both tools (knives/scrapers) and ornaments.
Field identification & locations
Identify in the field by its hardness (will scratch glass), conchoidal (shell-like) fracture, and opaque appearance. Found in desert regions, riverbeds, and volcanic ash deposits.
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