Blue banded agate nodules or geodes are not uncommon from The Carver Agate Field, but they most always seem to be blue from the outer rind inward to a white euhedral quartz center. Euhedral quartz are white or transparent visible crystals. The very center of this specimen and the area between the rind and the blue area are examples of euhedral quartz crystals. Usually, these crystals are seen in the center hollow of the cavity in a geode. In blue nodules, which do not have a hollow center or cavity, the center of the nodule, for some reason, is often white. Rock #4739 In this specimen, however, when the geode initially formed, it had no center–just a crystal lined cavity. Later, the blue colored part of this specimen was formed when a liquid or semi-liquid silica entered the original crystal lined cavity and filled it (almost) with blue banded agate […]

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