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lin murphy
Feb 2, 2009
Weathering patterns in desert granite. Heuco Tanks, Texas. Heucos and "plates" are common in the granitic rocks of the arid American SW. See Alabama Hills east of Whitney for classic "plates." Also known as "case hardening," these crusts are formed by the movement of ions in the rock by hydrological processes. The crusts are often oxides of iron and magnesium deposited on the surface by freezing and thawing cycles. These crusts are hard in dry periods and softer when it is wet--so watch out or you will make a heuco by pulling off a platy crust.  


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