sedimentary
Ocean Jasper (Orbicular Jasper)
Spherulitic Chalcedony (SiO2)
Hardness: 6.5-7 (Mohs); Color: Multi-colored greens, browns, and creams with orbicular (circular) patterns; Luster: Vitreous to waxy; Structure: Microcrystalline; Specific Gravity: 2.6-2.7
- Hardness
- 6
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Multi-colored greens, browns, and creams with orbicular (circular) patterns; Luster: Vitreous to waxy; Structure: Microcrystalline; Specific Gravity: 2.6-2.7
Formation & geological history
Formed as a result of rhythmic precipitation of silica around a nucleus within volcanic flows (rhyolite), typically in the littoral zone. This specific variety is found in Madagascar and dates back to the Cretaceous period.
Uses & applications
Primarily used for lapidary arts, jewelry (cabochons), and as a collector’s gemstone due to its unique patterns.
Geological facts
Ocean Jasper is only found on the coast of Madagascar and can only be mined during low tide. The original vein was discovered in 1999 and is now largely considered exhausted, making high-quality specimens increasingly rare.
Field identification & locations
Identify in the field by its distinct 'bullseye' or orbicular patterns and high hardness. It is exclusively found in the Analalava district of the Sofia region in northwest Madagascar. Collectors look for vibrant colors and 'flower-like' orbs.
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