sedimentary
Yellow Jasper
Silicon Dioxide with Iron inclusions (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Opaque mustard yellow to brownish-yellow; Lustre: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Opaque mustard yellow to brownish-yellow
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Opaque mustard yellow to brownish-yellow; Lustre: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.91
Formation & geological history
Formed from silica-rich fluids percolating through sedimentary rocks or volcanic ash, standardizing over millions of years. The yellow hue comes from concentrated Goethite or other iron oxyhydroxide inclusions. Often found in Precambrian to Cenozoic deposits.
Uses & applications
Primary use in lapidary work for cabochons, beads, and decorative carvings. Historically used for talismans, seals, and ornamental masonry. In construction, it can be a minor component in aggregate, but mostly used as a semi-precious gemstone.
Geological facts
Jasper was a favorite gem in the ancient world; its name can be traced back in Hebrew, Assyrian, Persian, Greek, and Latin. Yellow Jasper is specifically referred to as a 'stone of protection' in various folklore traditions and was used by ancient civilizations for its supposed grounding properties.
Field identification & locations
Identify by its solid mustard-yellow color, extreme hardness (will scratch glass), and opaque density (will not let light through even at thin edges). Commonly found in South Africa, Madagascar, Brazil, and the USA (notably Oregon and Idaho). Collectors should look for smooth, waxy surfaces in riverbeds or desert plains.
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