sedimentary
Jasper
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 on Mohs scale; Color: Red to brownish-red; Luster: Vitreous to dull; Crystal Structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Red to brownish-red
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Red to brownish-red; Luster: Vitreous to dull; Crystal Structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the accumulation of silica-rich fluids in volcanic ash or sedimentary beds. The red color is typically due to high concentrations of iron oxide (hematite). It can be found in formations dating from the Precambrian to more recent eras.
Uses & applications
Commonly used in jewelry (cabochons, beads), decorative stone carvings, seal stones, and as an ornamental component in architecture.
Geological facts
Jasper has been used as a gemstone since antiquity; it was mentioned in the Bible and used by ancient Minoans for seals. Its name comes from the Greek word 'iaspis', meaning 'spotted stone'.
Field identification & locations
Identify in the field by its smooth, waxy surface when wet, opaque transparency (light won't pass through), and its inability to be scratched by a steel knife. Commonly found in riverbeds and coastal gravels.
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