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 | |
Lizenzart: | Lizenzpflichtig |
Credit: | Science Photo Library / Natural History Museum, London |
Bildgröße: | 5125 px × 3410 px |
Modell-Rechte: | nicht erforderlich |
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