sedimentary
Jasper
Silicon dioxide (SiO2) with impurities
Hardness: 6.5-7 (Mohs); Color: Red, brown, and green mottling; Luster: Vitreous to waxy; Crystal Structure: Microcrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91.
- Hardness
- 6
- Color
- Red, brown, and green mottling
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Red, brown, and green mottling; Luster: Vitreous to waxy; Crystal Structure: Microcrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91.
Formation & geological history
Formed from the deposition of silica from water or volcanic ash. The red hues are caused by iron (III) inclusions, while green colors typically come from silicate minerals like chlorite. This specimen appears to be a water-worn river cobble.
Uses & applications
Used primarily for jewelry (cabochons, beads), decorative ornaments, and as a popular lapidary material for rock tumbling.
Geological facts
Jasper is an opaque variety of chalcedony. Historically, it was known as the 'supreme nurturer' in ancient cultures and has been used for seals and amulets since the Minoan civilization in Crete.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), its opaque nature, and the smooth, rounded surface indicating fluvial transport. Common in volcanic regions and ancient riverbeds worldwide.
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