mineral
Polished ocean jasper / orbicular jasper
Microcrystalline quartz (SiO₂), commonly with chalcedony, feldspar, and iron/manganese oxides
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; pale green, cream, gray, and brown with dark rounded orbicular patches; waxy to vitreous luster and no visible cleavage. The rounded, polished form is human-processed natural silica.
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Physical properties
Hardness about 6.5–7 Mohs; pale green, cream, gray, and brown with dark rounded orbicular patches; waxy to vitreous luster and no visible cleavage. The rounded, polished form is human-processed natural silica.
Formation & geological history
Forms when silica-rich volcanic fluids fill cavities and replace material in altered rhyolitic volcanic rocks; many ocean jasper specimens formed in Oligocene–Miocene volcanic terrain (~5–30 million years ago).
Uses & applications
Used for cabochons, carvings, beads, palm stones, and lapidary collections; not generally used as a construction stone.
Geological facts
Orbicular patterns result from concentric growth of chalcedony and associated minerals around nuclei, producing eye-like circles and mottling.
Field identification & locations
Identify by its dense feel, glassy/waxy polish, lack of cleavage, and hardness sufficient to scratch glass; classic ocean jasper comes from coastal Madagascar, while similar orbicular jasper occurs worldwide.
