sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs); Color: Yellow-brown/ochre due to iron oxide inclusions; Luster: Dull to waxy; Structure: Microcrystalline (Cryptocrystalline); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.9.
- Hardness
- 6
- Color
- Yellow-brown/ochre due to iron oxide inclusions
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Yellow-brown/ochre due to iron oxide inclusions; Luster: Dull to waxy; Structure: Microcrystalline (Cryptocrystalline); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.9.
Formation & geological history
Formed through the accumulation of fine-grained silica in organic or volcanic sediments. Frequently found as stream-rounded pebbles or nodules, its yellow/brown hue indicates the presence of goethite or limonite.
Uses & applications
Commonly used for lapidary work, jewelry (cabochons), talismans, and ornamental carvings. Historically used for making tools due to its hardness.
Geological facts
Jasper is an opaque variety of chalcedony. Yellow jasper specifically was historically associated with protection during travel and spiritual guidance.
Field identification & locations
Look for a smooth, water-worn texture with an opaque body that does not transmit light. Found in riverbeds, beaches, and desert plains worldwide. Collectors value stones with intense, uniform color or unique patterns.
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