sedimentary
Agate
Silicon dioxide (chalcedony, SiO2)
AI-generated identification · may be incorrectHardness of 6.5-7 on the Mohs scale, waxy luster, and trigonal crystal system with distinct concentric banding.
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Physical properties
Hardness of 6.5-7 on the Mohs scale, waxy luster, and trigonal crystal system with distinct concentric banding.
Formation & geological history
Formed by the deposition of silica from groundwater in cavities of igneous and sedimentary rocks over millions of years.
Uses & applications
Widely used in ornamental carvings, jewelry, and polished collector specimens.
Geological facts
Agate is a microcrystalline variety of quartz that often forms within ancient volcanic vesicles.
Field identification & locations
Identified by its translucent banded layers and conchoidal fracture; commonly found worldwide.
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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