sedimentary
Jasper
Silicon dioxide (SiO2) with iron oxide impurities
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, earthy tones; Luster: Vitreous to waxy (when polished); Crystal structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91
- Hardness
- 6
- Color
- Reddish-brown, earthy tones
- Luster
- Vitreous to waxy (when polished)
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, earthy tones; Luster: Vitreous to waxy (when polished); Crystal structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91
Formation & geological history
Usually forms from the precipitation of silica from groundwater in sedimentary environments, often associated with volcanic activity where silica-rich fluids permeate porous rocks. It can be found in various geological ages ranging from Precambrian to recent deposits.
Uses & applications
Commonly used for lapidary work, jewelry (cabochons and beads), ornamental carvings, and as a collector's stone. Historically used for making tools due to its hardness and sharp fracture edges.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning 'spotted stone'. It is known as a 'nurturing stone' in metaphysical circles and has been used for millennia by civilizations like the Egyptians and Minoans.
Field identification & locations
Identify in the field by its opacity (unlike translucent agate), high hardness (cannot be scratched by a steel knife), and smooth, rounded water-worn appearance in riverbeds. Found globally, with notable deposits in India, Brazil, and the Western USA.
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