sedimentary
Jasper containing Agate (Jaspagate)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Mottled red, brown, and green with waxy luster; Crystal Structure: Microcrystalline (trigonal); Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Mottled red, brown, and green with waxy luster
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Mottled red, brown, and green with waxy luster; Crystal Structure: Microcrystalline (trigonal); Specific Gravity: 2.6-2.9
Formation & geological history
Formed from silica-rich groundwater filling cavities in volcanic or sedimentary rocks, often associated with iron oxidation which provides the reddish-brown hues. Most specimens are from the Phanerozoic eon.
Uses & applications
Commonly used in lapidary work for cabochons, beads, and tumbled stones. Occasional industrial use as a hard grinding medium.
Geological facts
Jasper is an opaque variety of chalcedony. When it mixed with translucent agate, it is colloquially known as 'Jaspagate'. The red color is typically due to inclusion of hematite.
Field identification & locations
Identify in the field by its waxy luster, smoothness when water-worn, and its inability to be scratched by a steel knife. Commonly found in riverbeds and gravel pits in volcanic regions.
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