
mineral
Polished green agate/chalcedony
Microcrystalline quartz (SiO₂), likely chrysoprase- or moss-agate-like chalcedony
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent blue-green to gray-green with a waxy/glassy luster and no visible cleavage. Its rounded form is tumbled and polished, so crystal structure is cryptocrystalline rather than visibly crystalline.
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Physical properties
Hardness 6.5–7 Mohs; translucent blue-green to gray-green with a waxy/glassy luster and no visible cleavage. Its rounded form is tumbled and polished, so crystal structure is cryptocrystalline rather than visibly crystalline.
Formation & geological history
Silica-rich groundwater filled cavities or fractures in volcanic rock, where chalcedony precipitated in layers or patches. Such agates commonly formed during the Cenozoic or older volcanic episodes, depending on locality.
Uses & applications
Used for cabochons, beads, carvings, ornaments, and inexpensive jewelry; polished pieces are popular for collecting and metaphysical displays.
Geological facts
Green coloration may come from nickel-bearing chalcedony (chrysoprase) or inclusions of chlorite, celadonite, or other minerals. Natural color zoning and translucency help distinguish it from dyed glass or resin.
Field identification & locations
Check for translucency, subtle internal banding or inclusions, a waxy surface, and quartz-like hardness; it should resist scratching by steel but not by quartz. Common sources include Brazil, Uruguay, India, Madagascar, Australia, and the western United States.
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