The large to giant gypsum crystals of the Pulpi Geode, Mina Rica near Pilar de Jaravia in Southeastern Spain are a prime example for an extraordinary large textbook geode.

Crystal lined geodes are a quite common geological phenomen, particulary in volcanic rocks. The rock is cooling down and the gas content of the original melt tries to excape in small and sometimes large bubbles. Finally the rock crystallizes and the gas bubbles are trapped in the 'frozen' rock. These gas bubbles remain as more or less rounded empty voids over considerable geological times, before mineral rich hydrothermal fluids starts to depose minerals in these vugs. Eventually crystals grow and the vug or geode fills up with well developed crystals.

Myriads of those crystal geodes exist and are often displayed and sold on mineral shops and shows. Just think of all these purple amethyst geodes from Brazil or the beautiful zeolites from the Poona - Bombay district in India. But hardly ever do geodes reach giant dimensions. In the Mina Rica in Southern Spain they did. This once flourishing iron, lead and silver mine, which exported its mineral wealth to England and Germany, was finally closed down in the 1970ties. However some miners continued to believe in the treasures of the mine and eventually started exploration of the old mine workings on their own. In December 1999 they succeeded and discovered a remarkable geode...

The giant Pulpi geode, which can be accessed by a tedious trip through abandoned narrow adits and stopes only, has an inner length of 8 m and a width of 1,8 m, while the medium height is 1,7 m. Its outer appearance is that of an almost perfect elongated egg with a length of roughly 10 m. The geode is filled with water clear gypsum crystals of a medium size of 0.5 m, whereas the maximum recorded crystal size is two meters. No other minerals are known to occur, though in other parts of the mine a much more diversified mineralogy including nice celestite sprays have been found.

In the past years the 'Gran Pulpi Geoda' was investigated thoroughly by various spanish geoscientists and in fact this locality seems to be one of the best documented giant crystal occurences in existence. However it was found, that only few visitors raise the humidity in the geode from 65 % to almost 100 %, which is not good for a delicate and water soluble mineral such as gypsum. So the planned touristic exploitation of the cave was put on hold and only scientist are allowed to visit the geode for the time being.