sedimentary
Agate
Silicon dioxide (SiO2)
AI-generated identification · may be incorrectMohs hardness of 6.5 to 7. Color varies from yellow, orange, to brown with translucent to waxy luster. Microcrystalline quartz structure with no cleavage and a specific gravity of 2.6.
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Physical properties
Mohs hardness of 6.5 to 7. Color varies from yellow, orange, to brown with translucent to waxy luster. Microcrystalline quartz structure with no cleavage and a specific gravity of 2.6.
Formation & geological history
Forms by the deposition of silica from groundwater in cavities of igneous and sedimentary rocks. Geologically ancient, often millions of years old.
Uses & applications
Widely used in ornamental jewelry, decorative carvings, and precision instruments due to its durability.
Geological facts
Agate is a banded variety of chalcedony. Ancient civilizations valued it as a talisman and for making seals.
Field identification & locations
Identify by its waxy luster, conchoidal fracture, and subtle banding. Found globally in volcanic rock cavities and river gravels.
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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
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Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
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Sandstone
Arenite
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Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary