These strange floater balls of gypsum crystals formed deep in clay beds in the floodway of the Red River, and have been mined there (with a lot of labor) since the 60s. They are truly beautiful, particularly when you have just one or two twinned crystals rising from the rest of the ball in isolation, as here.
Attribution: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0
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