sedimentary
Jasper
Silicon Dioxide (SiO2) with iron oxide impurities
Hardness: 6.5-7 (Mohs), Color: Reddish-brown, Luster: Dull to greasy, Crystal structure: Microcrystalline/Trigonal (Cryptocrystalline), Cleavage: None, Specific gravity: 2.58-2.91
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Reddish-brown, Luster: Dull to greasy, Crystal structure: Microcrystalline/Trigonal (Cryptocrystalline), Cleavage: None, Specific gravity: 2.58-2.91
Formation & geological history
Formed through the accumulation of fine-grained silica in sedimentary environments like seafloors, often associated with volcanic activity or hydrothermal processes. The brown/red hue comes from hematite or goethite inclusion.
Uses & applications
Used primarily as decorative stones, in jewelry (cabochons), or as pocket stones. Historically used for making tools and seals due to its hardness and conchoidal fracture.
Geological facts
Jasper is an opaque variety of chalcedony. It has been used in jewelry since ancient civilizations in Mesopotamia and Egypt. It is mentioned in several ancient texts and religious scriptures as a protective stone.
Field identification & locations
Look for a smooth, waxy, or dull texture that cannot be scratched by a steel pocket knife. Identifiable by its opacity (it will not let light through even at the edges) and smooth, rounded surface when found in riverbeds.
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