Gypsum

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The Red River Floodway in the Winnipeg Metro Region of Manitoba, Canada is one of the most famous Selenite (a variety of Gypsum) localities in the whole of North America. Essentially a drainage channel, it is only in the floodway that sufficient depth is reached to expose the Pleistocene Lake Agassiz clay bed within which the Selenite occurs. These fascinating specimens are made up from spherical clusters of Gypsum whose outermost layer is encrusted with Selenite crystals, the transparent variety of Gypsum, projecting outwards. As Gypsum is a very soft mineral the collection and care of these beautiful crystallizations needs to be undertaken carefully which is why really fine specimens like this one from Martin Kershaw's collection (no. 802) are so special. It has just minimal damage to the edges of three or four crystals but this really is trivial. The larger Selenite crystals reach 2.7 cm in length.