Tuesday, August 11, 2009

Devils Tower

Those of you who were just there probably know this:
Devils Tower is made of phonolite porphyry. Phonolite refers to the ringing of the rock when a small slab is struck, and its ability to reflect sound. Porphyry refers to its texture, large crystals of feldspar embedded in a mass of smaller crystals.
From NPS.gov.

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