sedimentary
Jasper
Silicon Dioxide (SiO2) with iron and magnesium inclusions
Hardness: 6.5–7 (Mohs scale). Color: Opaque with a range of dull greens, mustard yellows, and earthy browns frequently seen in this variety. Luster: Vitreous to waxy. Crystal Structure: Hexagonal/Trigonal (microcrystalline/cryptocrystalline crypto-aggregates). Cleavage: None. Specific Gravity: 2.58–2.91.
- Hardness
- 6
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5–7 (Mohs scale). Color: Opaque with a range of dull greens, mustard yellows, and earthy browns frequently seen in this variety. Luster: Vitreous to waxy. Crystal Structure: Hexagonal/Trigonal (microcrystalline/cryptocrystalline crypto-aggregates). Cleavage: None. Specific Gravity: 2.58–2.91.
Formation & geological history
Formed through the accumulation of fine-grained silica (quartz) and chalcedony in sedimentary environments, often associated with volcanic activity where mineral-rich fluids infiltrate volcanic ash or sediments. The earthy tones result from impurities like iron oxides and silicates trapped during crystallization.
Uses & applications
Primarily used in jewelry for beads, cabochons, and bracelets. Due to its durability and ability to take a high polish, it is also used for small ornamental carvings and decorative inlays.
Geological facts
Jasper has been used as a gemstone since antiquity; it was known in ancient Mesopotamian and Minoan civilizations as a sacred and protective stone. Unlike clear quartz, its 'cloudy' or opaque appearance is caused by a high percentage of mineral impurities—sometimes up to 20%.
Field identification & locations
Identify in the field by its opacity (it does not transmit light even on thin edges), its conchoidal (shell-like) fracture, and its high hardness (it will scratch glass but cannot be scratched by a steel knife). Common locations include India, Russia, Brazil, and the USA.
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