sedimentary
Jasper
Jasper (Silicon Dioxide, SiO2)
Hardness: 6.5-7 (Mohs); Color: Yellow, ochre, brown, and dark green/black banding; Luster: Dull to vitreous; Crystal Structure: Microcrystalline/Cryptocrystalline (Hexagonal/Trigonal); Cleavage: None, usually conchoidal fracture.
- Hardness
- 6
- Color
- Yellow, ochre, brown, and dark green/black banding
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Yellow, ochre, brown, and dark green/black banding; Luster: Dull to vitreous; Crystal Structure: Microcrystalline/Cryptocrystalline (Hexagonal/Trigonal); Cleavage: None, usually conchoidal fracture.
Formation & geological history
Formed from the deposition of silica-rich fluids in volcanic or sedimentary environments. The yellow and brown hues are caused by iron oxides (goethite or limonite). These often date back to the Proterozoic or Mesozoic eras.
Uses & applications
Commonly used in lapidary work for making cabochons, beads, and ornemental carvings. Larger pieces are used as garden accents or decor items.
Geological facts
Jasper is a variety of chalcedony that is opaque due to high mineral impurities (up to 20%). Yellow jasper was historically known as a stone of protection and travel.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and smooth, waxy feel when wet. Found in riverbeds and desert environments globally, notably South Africa, India, and the USA (Pacific Northwest).
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