sedimentary
Yellow Jasper
Silicon Dioxide (SiO2) with goethite or limonite inclusions
Hardness: 6.5-7 on Mohs scale; Color: Mustard yellow to brownish-yellow; Luster: Dull or waxy to vitreous; Crystal Structure: Hexagonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Mustard yellow to brownish-yellow
- Luster
- Dull or waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Mustard yellow to brownish-yellow; Luster: Dull or waxy to vitreous; Crystal Structure: Hexagonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.91
Formation & geological history
Forms when silica-rich fluids permeate through volcanic ash or sedimentary beds, precipitating microcrystalline quartz and trapping iron oxides during the silicification process.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons, beads), decorative carvings, and as a collector's specimen. Historically used for making tools and weapons due to its conchoidal fracture.
Geological facts
Jasper is an opaque variety of chalcedony. The name 'jasper' comes from the Greek word 'iaspis', meaning 'spotted stone.' Yellow jasper was traditionally used as a protective stone by shamans and ancient travelers.
Field identification & locations
Identify by its yellow-brown color, opacity (light will not pass through even thin edges), and conchoidal (shell-like) fracture patterns. Frequently found in riverbeds or desert regions globally, especially in Oregon (USA), South Africa, and Madagascar.
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