sedimentary
Red Jasper (Silicate Chert)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs); Color: Deep red to maroon with dark streaks; Luster: Dull to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Deep red to maroon with dark streaks
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Deep red to maroon with dark streaks; Luster: Dull to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.9
Formation & geological history
Formed through the accumulation of fine-grained silica in hydrothermal veins or as sedimentary deposits where iron minerals oxidize to create the red pigment. Often associated with volcanic activity or ancient seabed deposits.
Uses & applications
Used primarily as a gemstone for jewelry (cabochons), lapidary carvings, decorative landscaping, and occasionally in industrial grinding media due to its hardness.
Geological facts
Red jasper has been used for millennia for amulets and seals. In ancient Egypt, it was often associated with the 'Blood of Isis' and used for protective jewelry. It is a variety of chalcedony that obtains its color from hematite (iron oxide).
Field identification & locations
Identify by its waxy-to-dull luster, extreme hardness (it will scratch glass), and characteristically smooth, curved fracture surfaces. Commonly found in riverbeds, deserts, and areas with volcanic soil or ancient sedimentary basalts.
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