Opal ‘Pineapple’

This opal ‘pineapple’ has nothing to do with the fruit – the term is only a visual description. The opal is made of silicon dioxide with water.

This unusual pineapple-shaped object is thought to be a replacement (or pseudomorph) of one mineral by another before becoming an opal. Once thought to be a replacement of glauberite (sodium sulphate), it is now thought to be a replacement of crystals of the water-bearing calcium carbonate, ikaite. Ikaite only grows under very cold, glacial conditions and then rapidly changes to waterless calcite. The calcite in this specimen was then replaced by purple and green-blue opal.

Opal ‘pineapples’ with their distinctive radiating pointed forms, are only found at the White Cliffs opal field. These curiosities are very valuable and are much prized by collectors. Albert Chapman purchased this specimen in the 1930s.

Andamooka, South Australia, Australia. 4.5 x 5 x 2.5 cm. D.50438. Albert Chapman Collection.