sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7.0 (Mohs scale); Color: Red, brown, or earthy tones; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.58-2.91.
- Hardness
- 6
- Color
- Red, brown, or earthy tones
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6.5-7.0 (Mohs scale); Color: Red, brown, or earthy tones; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.58-2.91.
Formation & geological history
Formed through the infiltration of silica-rich fluids into volcanic ash or fine sedimentary material, often colored by iron oxide. It typically dates from the Proterozoic to Cenozoic eras.
Uses & applications
Commonly used in jewelry (cabochons), ornamentation, lapidary arts, and as a collector's stone. Historically used for seal stones and tools.
Geological facts
Jasper is an opaque variety of chalcedony. The name is derived from the Greek 'iaspis', meaning 'spotted stone'. It was one of the stones used in the Breastplate of Aaron.
Field identification & locations
Identify in the field by its waxy-to-dull luster, opacity, and conchoidal fracture. Often found as rounded pebbles in stream beds or coastal beaches where water has polished them.
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