sedimentary
Yellow Jasper
Silicon Dioxide (SiO2) with iron hydroxides (Goethite)
Hardness: 6.5–7 on the Mohs scale; Color: mustard yellow to brownish-yellow; Luster: Dull to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91
- Hardness
- 6
- Color
- mustard yellow to brownish-yellow
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6.5–7 on the Mohs scale; Color: mustard yellow to brownish-yellow; Luster: Dull to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91
Formation & geological history
Formed through the infiltration of silica-rich fluids into volcanic ash or fine sedimentary layers. The yellow coloration is derived from iron impurities, typically occurring in Precambrian to Cenozoic geological ages.
Uses & applications
Used primarily for lapidary work, cabochons, beads, decorative carvings, and as a collector's gemstone. Historically used for ornaments and talismans.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Greek 'iaspis', meaning 'spotted stone'. It was one of the stones used in the breastplate of the high priest in ancient biblical times.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel knife), smooth conchoidal fracture, and absolute opacity. Commonly found in South Africa, India, and the Western USA (Oregon, Idaho).
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