mineral
Agate
Cryptocrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 6.5-7 on the Mohs scale. Characterized by fine grain and bright colors or patterns, often translucent as seen in the backlighting. Waxy to vitreous luster.
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Physical properties
Hardness of 6.5-7 on the Mohs scale. Characterized by fine grain and bright colors or patterns, often translucent as seen in the backlighting. Waxy to vitreous luster.
Formation & geological history
Forms primarily in cavities of eruptive rocks or ancient lavas, where silica-rich waters percolate and deposit microcrystalline quartz in concentric layers.
Uses & applications
Used historically and currently for hardstone carving, cabochons, beads, and as decorative, polished specimens for collectors.
Geological facts
Agate is named after the Achates River in Sicily, where it was discovered by the Greek philosopher Theophrastus.
Field identification & locations
Identify by its translucence when held to light, characteristic banding (though sometimes subtle in tumbled stones), and conchoidal fracture. Very common worldwide, including volcanic areas like the Ethiopian highlands.
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Calcite (CaCO₃), likely fluorite (CaF₂), with possible quartz and iron/manganese oxides
mineral
Septarian Pebble
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Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
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Pegmatite with Tourmaline and Quartz
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