sedimentary
Jasper (specifically Yellow and Red Jasper/Chert)
Silicon Dioxide (SiO2) with Iron Oxide inclusions
Hardness: 6.5–7 on Mohs scale; Color: Opaque yellow and red-orange; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.91
- Hardness
- 6
- Color
- Opaque yellow and red-orange
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Opaque yellow and red-orange; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.91
Formation & geological history
Formed from the deposition of silica-rich fluids in sedimentary environments or volcanic ash. The distinct red and yellow colors are the result of varying concentrations and oxidation states of iron (hematite for red, goethite/limonite for yellow). Most specimens are millions of years old.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons and beads), decorative ornaments, and as a collector's specimen. In ancient times, it was used for making tools due to its sharp conchoidal fracture.
Geological facts
Jasper has been used as a gemstone since antiquity and is mentioned in many historical religious texts. Its name is derived from the Greek word 'iaspis', meaning spotted stone. It is a microcrystalline variety of quartz.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife), smooth waxy feel when wet, and smooth, curved (conchoidal) breakage surfaces. It is commonly found in riverbeds and desert environments throughout the Western United States and India.
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