sedimentary
Red Jasper (Opaque Chalcedony)
Silicon Dioxide (SiO2) with Hematite inclusions
Hardness: 6.5–7 (Mohs scale); Color: Brick red to brownish-red with occasional cream or black veins; Luster: Vitreous to waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); 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: Brick red to brownish-red with occasional cream or black veins; Luster: Vitreous to waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91
Formation & geological history
Formed through the precipitation of silica from thermal water or volcanic activity within sedimentary or metamorphic environments. Its vibrant red color is caused by the presence of iron oxide (hematite) during the silicification process. Age varies by deposit but common throughout geological history.
Uses & applications
Used widely in lapidary for cabochons, beads, and decorative carvings. Historically used for making tools like scrapers and arrowheads due to its conchoidal fracture. Also popular in metaphysical collections and as an ornamental stone in jewelry.
Geological facts
Jasper was a favorite gem in the ancient world; its name can be traced back to Greek, Hebrew, and Persian roots meaning 'spotted or speckled stone.' It is a member of the chalcedony family, specifically defined by its opacity and high mineral inclusion content.
Field identification & locations
Identify in the field by its opacity (it does not transmit light even on thin edges), its smooth conchoidal fracture, and it cannot be scratched by a steel knife. Common locations include the USA (Oregon, Idaho), Brazil, India, and Australia. Collectors should look for 'picture' patterns or intense uniform color.
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