Geode in thin section,close-up,viewed in transmitted polarised light. A geode forms when silica (SiO2) 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. Here,a core of quartz (the crystalline form of silica) can be seen. The banded arrangement of crystals are a result of changes in pressure,temperature,and mineral content occurring during the formation process. Magnification: x3.8 when printed 10 centimetres wide | |
Lizenzart: | Lizenzpflichtig |
Credit: | Science Photo Library / Wiersma, Dirk |
Bildgröße: | 5186 px × 4082 px |
Modell-Rechte: | nicht erforderlich |
Eigentums-Rechte: | nicht erforderlich |
Restrictions: | - |