Mineral / Sedimentary
Jasper (specifically Brecciated or Agated Jasper)
Silicon Dioxide (SiO2) - Chalcedony with impurities
Hardness: 6.5-7 (Mohs scale); Color: Mottled red, brown, and grey/white; Luster: Vitreous to waxy (when polished); Crystal Structure: Microcrystalline (trigonal); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Mottled red, brown, and grey/white
- Luster
- Vitreous to waxy (when polished)
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Mottled red, brown, and grey/white; Luster: Vitreous to waxy (when polished); Crystal Structure: Microcrystalline (trigonal); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the deposition of silica from water into subterranean cavities or cracks in volcanic rocks or sedimentary environments. The mottled appearance suggests a brecciation process where original rock fragments are cemented together by subsequent silica deposits.
Uses & applications
Primarily used for lapidary work, jewelry (cabochons, beads), decorative ornaments, and as a 'healing stone' in metaphysical practices. Historically used for making tools and seals.
Geological facts
Jasper is an opaque variety of chalcedony. The red coloration is typically caused by iron inclusions (hematite). It has been a popular gemstone since antiquity, mentioned in various historical texts including the Bible and Greek mythology.
Field identification & locations
Identify in the field by its opacity (unlike translucent agate), high hardness (cannot be scratched by a steel knife), and smooth, waxy feel when water-worn. Common in riverbeds and desert environments globally, notably in India, Brazil, and the USA.
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