sedimentary
Jasper
Silicon dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, yellow, ochre; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Reddish-brown, yellow, ochre
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, yellow, ochre; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the circulation of silica-rich fluids in volcanic ash or sedimentary rocks. The yellow and reddish-brown colors are caused by the infiltration of iron oxides (limonite and hematite) during or after the mineralization process.
Uses & applications
Used primarily as decorative carvings, gemstones for jewelry (cabochons), and as a collector's item due to its variety of patterns.
Geological facts
Jasper has been used by humans for thousands of years; it was a favorite gem in the ancient world, referenced in many historical texts and used for cylinder seals and amulets in Mesopotamia.
Field identification & locations
Identify in the field by its hardness (will scratch glass), smooth waxy feel when polished, and lack of cleavage. Often found near areas of volcanic activity or in riverbeds where water has smoothed the exterior.
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