sedimentary
Jasper
Jasper (Silicon Dioxide, SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to greenish-brown; Luster: Vitreous to dull; Crystal Structure: Trigonal (Microcrystalline); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Brownish-red to greenish-brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to greenish-brown; Luster: Vitreous to dull; Crystal Structure: Trigonal (Microcrystalline); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the infiltration of silica-rich fluids into volcanic ash or fine-grained sediments during diagenesis or hydrothermal activity. Often found in Precambrian formations or as stream-worn pebbles.
Uses & applications
Commonly used for lapidary work, decorative cabochons for jewelry, small ornaments, and as a popular collected pebble for rockhounds.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Old French 'jaspre', meaning 'spotted or speckled stone'. Historically, it was used for cylinder seals and as amulets for protection.
Field identification & locations
Identify in the field by its high hardness (won't be scratched by a knife) and smooth, waxy surface when wet. Commonly found along riverbeds, glacial tills, and beaches.
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