Rhyolitic geode. Cut surface of a geode displaying the host rock rhyolite (green), chalcedony (blue- white) and haematite (red). Geodes form when a ho

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Rhyolitic geode. Cut surface of a geode displaying the host rock rhyolite (green), chalcedony (blue- white) and haematite (red). Geodes form when a hollow in a rock becomes filled with mineral crystals that grow inward to the centre of the hollow. Rhyolite is a volcanic rock formed by the cooling of lava on the Earth's surface. Chalcedony is a term for many cryptocrystalline quartz (silicon dioxide) gemstones, including agate. The colours are derived from impurities in the mineral. Haematite is a form of iron oxide. This geode came from the Esterel region on the Mediterranean coast in France.

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Size: 3720px × 4728px
Photo credit: © DIRK WIERSMA/SCIENCE PHOTO LIBRARY / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: agate, chalcedony, cryptocrystalline, crystalline, cut, dioxide, gemstone, geode, haematite, horizontal, host, impure, impurities, lithophyses, mineral, natural, polished, quartz, rhyolite, rhyolitic, rock, rocks, section, sectioned, semi-precious, silicon, sliced, stone, stones, surface