Calcite is abundant, and often is the only mineral in a cavity. It generally grows directly on the vugh walls, but also occurs on phillipsite, and may have phillipsite, erionite or barite growing on it. Perhaps the commonest form is clear to white “castles” of a rounded tapering crystal with many parallel overgrowths. These rarely show sharp terminations. Single crystals are less common, usually very small. Some calcite occurs in masses and singles like stacked bricks, more or less flattened. Some have a white centre and clear overgrowth, others are entirely clear. The trigonal system in shown by bevelled edges and triple-faced termination. Some calcite is fluorescent under longwave ultraviolet light.
Below: Calcite, Moeraki Point, Otago Region, New Zealand. Width of view 9mm. Shown under longwave ultraviolet light.
