sedimentary
Agate
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness 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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Other sedimentary specimens
Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image
fossil
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary