sedimentary
Jasper Agate (specifically Brecciated Jasper)
Silicon Dioxide (SiO2) with iron oxide and clay impurities
Hardness: 6.5-7 Mohs; Color: Mottled red, brown, and tan; Luster: Vitreous to waxy; Crystal structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.91
- Hardness
- 6
- Color
- Mottled red, brown, and tan
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Mottled red, brown, and tan; 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-rich fluids within volcanic or sedimentary cavity rocks. The 'brecciated' look occurs when the rock is fractured by tectonic activity and later re-cemented by quartz or chalcedony. Many specimens date from the Mesozoic or Cenozoic eras.
Uses & applications
Primarily used for lapidary work, jewelry (pendants, beads), ornamental carvings, and as a 'grounding stone' in metaphysical collections.
Geological facts
Jasper is an opaque variety of chalcedony. The name 'brecciated' comes from the Italian word 'breccia,' meaning 'broken gravel,' referring to its fragmented appearance. It has been used since antiquity for seals and talismans.
Field identification & locations
Identify by its opacity, earthy colors, and lack of visible crystals. It is commonly found in the United States (Oregon, Idaho), Brazil, and South Africa. For collectors, look for high contrast between the fractured pieces and the 'cement' holding them together.
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