sedimentary
Agate
Silicon Dioxide (SiO2)
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline quartz structure, conchoidal fracture, variable colors often showing concentric bands.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline quartz structure, conchoidal fracture, variable colors often showing concentric bands.
Formation & geological history
Formed mainly in cavities of eruptive rocks or ancient lavas through the deposition of silica from groundwater solutions over millions of years.
Uses & applications
Used in ornamental objects, jewelry, polished specimens, mortars and pestles for laboratory use, and by collectors.
Geological facts
Agate was named by Theophrastus, a Greek philosopher, after the Achates River in Sicily where the stones were first found.
Field identification & locations
Identified by its waxy luster, hardness that scratches glass, and characteristic banded patterns; commonly found worldwide, particularly in Brazil, Uruguay, and the Lake Superior region of the US.
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Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
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Generic Pebble / Rock Fragment
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Banded Siltstone / Mudstone Pebble
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Sedimentary Sandstone
Arenite (Sedimentary Rock)
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