sedimentary
Jasper (likely Brown or Brecciated)
Jasper (Silicon Dioxide, SiO2)
Hardness: 6.5–7 (Mohs scale); Color: Brown, black, and reddish-brown banded/mottled patterns; Luster: Vitreous to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58–2.91
- Hardness
- 6
- Color
- Brown, black, and reddish-brown banded/mottled patterns
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Brown, black, and reddish-brown banded/mottled patterns; Luster: Vitreous to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58–2.91
Formation & geological history
Formed through the deposition of silica from water or hydrothermal solutions, often replacing organic matter or volcanic ash. The brown and black coloring typically comes from iron oxide (hematite or goethite) or manganese inclusions. It can span eras from the Precambrian to recent periods.
Uses & applications
Commonly used in lapidary work for cabochons, beads, and tumbled stones. In industry, it is sometimes used as an abrasive or in decorative tiling and landscaping due to its hardness and aesthetic appeal.
Geological facts
Jasper is an opaque variety of chalcedony. The name is derived from the Greek word 'iaspis', meaning 'spotted stone.' Ancient civilizations often used it for cylinder seals and amulets, believing it provided protection and stability.
Field identification & locations
Identify in the field by its high hardness (it will scratch glass), opaque appearance (even on thin edges), and conchoidal fracture patterns. It is frequently found in riverbeds, desert pavements, and near silica-rich volcanic or sedimentary outcrops globally, with significant deposits in the USA, Brazil, and India.
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