sedimentary
Agate
Silicon dioxide (chalcedony, SiO2)
AI-generated identification · may be incorrectHardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, and conchoidal fracture with banded color patterns.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, and conchoidal fracture with banded color patterns.
Formation & geological history
Formed by the deposition of silica from groundwater in cavities of igneous and sedimentary rocks over millions of years.
Uses & applications
Used widely in ornamental carvings, jewelry, lapidary arts, and precision instruments.
Geological facts
Agate was highly prized in ancient civilizations like Egypt and Greece for amulets and seal rings, and it is often found lining ancient volcanic gas bubbles.
Field identification & locations
Easily identified by its distinctive concentric banding and smooth, waxy feel; commonly found in riverbeds and volcanic regions 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
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary