sedimentary
Jasper (Mookaite style)
Jasper (Silica-rich Microcrystalline Quartz, SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Variegated red, yellow, mustard, and brown; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.5–2.9
- Hardness
- 6
- Color
- Variegated red, yellow, mustard, and brown
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Variegated red, yellow, mustard, and brown; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.5–2.9
Formation & geological history
Formed via the sedimentation of radiolaria (microscopic marine organisms) whose skeletal remains are composed of silica. These organisms settle in shallow marine environments and undergo silicification. Many variegated jaspers date back to the Cretaceous period (approx. 145–66 million years ago).
Uses & applications
Primarily used in jewelry as cabochons, decorative carvings, lapidary arts, and as a popular collector's specimen due to its vibrant patterns and high polish.
Geological facts
Jasper has been used as a gemstone since antiquity and is mentioned in the Bible and Norse mythology. Variegated varieties like this are often called 'polychrome' or 'mookaite' depending on their specific Australian or Madagascan origin, indicating an abundance of iron oxide impurities.
Field identification & locations
Identify in the field by its hardness (it can scratch glass), opaque nature, and smooth, shell-like (conchoidal) fractures. Common locations include the Kennedy Ranges in Australia, Madagascar, and various riverbeds in the American West.
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