Unweathered Lake Superior agate. Agate is an aggregate of different forms of silica (SiO2) that have formed concentric bands within a geode. A geode f

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Unweathered Lake Superior agate. Agate is an aggregate of different forms of silica (SiO2) that have formed concentric bands within a geode. A geode forms when the silica precipitates from liquid onto the inside surface of an empty pocket in a host rock. The outer layers are variegated forms of chalcedony (amorphous or non-crystalline silica), with the layers becoming more crystalline towards the centre. These agates are stained by iron and found on the shores of Lake Superior, USA. Specimen from a mine in the Keweenaw Peninsula, Michigan, USA.

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Size: 5125px × 3410px
Photo credit: © NATURAL HISTORY MUSEUM, LONDON/SCIENCE PHOTO LIBRARY / Alamy / Afripics
License: Licensed
Model Released: No

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