Ventifacts are formed when a rock remains in one position on the desert floor for a long period without being disturbed and is faceted by wind-blown sand. Typically, ventifacts have two or more flat faces - facets - with a sharp ridge separating one facet from another. The "textbook" example is a dreikanter, three cornered and symmetrical, though these are not often encountered.

Different in shape, this small ventifact has two sharply faceted sides with a separating ridge.

Many ventifacts form in Banning Pass, California, where this was collected. The pass separates the Los Angeles Basin from the Mojave Desert to the east, and is a funnel for strong winds, with wind turbine farms taking advantage of the blast to generate electricity. There is an ample supply of sand, as the pass separates the two highest peaks in Southern California, Mt. San Jacinto on the south, where the top is accessible via the Palm Springs tram, and Mt. San Gorgonio on the north. The San Andreas Fault runs roughly east-west through the pass. At the east end, Garnet Hill is covered in spectacular ventifacts. Many are large, granitic, and well sand blasted. Since Garnet Hill is a regular geology teaching, research and field trip stop, we don't collect there.

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ventifacts

ventifact - hand specimen of a rock faceted by wind-blown sand

$ 7.50