sedimentary
Agate
Silicon dioxide (SiO2)
AI-generated identification · may be incorrectMohs hardness of 6.5 to 7, waxy to vitreous luster, cryptocrystalline structure with distinct color banding, and conchoidal fracture.
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Physical properties
Mohs hardness of 6.5 to 7, waxy to vitreous luster, cryptocrystalline structure with distinct color banding, and conchoidal fracture.
Formation & geological history
Forms by the deposition of silica from groundwater in cavities of igneous and sedimentary rocks over millions of years.
Uses & applications
Widely used in jewelry, decorative ornaments, ornate carvings, and industrial pivot bearings or mortars.
Geological facts
Agate is a variety of chalcedony that often forms in ancient volcanic vesicles, preserving vibrant multicolored bands.
Field identification & locations
Identified by its waxy luster, microcrystalline bands, and inability to be scratched by steel. Found globally, notably in Brazil and the USA.
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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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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