mineral
Polished ocean jasper (orbicular jasper)
Silicified rhyolite, composed mainly of microcrystalline quartz (SiO₂)
AI-generated identification · may be incorrectPolished egg-shaped specimen with gray-green chalcedony and cream-to-yellow orbicular patterns. Quartz hardness is about 6.5–7 Mohs; it has a waxy to vitreous luster and no visible cleavage. The exact variety is uncertain from the photo alone.
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Physical properties
Polished egg-shaped specimen with gray-green chalcedony and cream-to-yellow orbicular patterns. Quartz hardness is about 6.5–7 Mohs; it has a waxy to vitreous luster and no visible cleavage. The exact variety is uncertain from the photo alone.
Formation & geological history
A silica-rich volcanic rock later altered and silicified, with orb-like patterns formed during mineral deposition. Ocean jasper is associated with Oligocene–Miocene volcanic rocks of Madagascar.
Uses & applications
Polished for ornaments, cabochons, beads, and collecting; jasper is also used for small decorative objects.
Geological facts
Ocean jasper is prized for its concentric orb patterns, which can resemble eyes or flowers.
Field identification & locations
Look for rounded, contrasting orb-like markings within opaque to translucent chalcedony; this polished specimen cannot be field-identified by texture alone. Classic ocean jasper comes from the Marovato area of northwest Madagascar.
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