The Stone

The 11-ton block came from Raymond, California, via Cold Springs, Minnesota, and is commonly called Academy Black granite. The finished sculpture weighs 6212 pounds. This type of stone weighs about three times as much as water. The material is, in fact, not granite, but quartz diorite, and is 100 million years old. A geological analysis by Jeff Thole (Macalester geology department) showed that it is a medium-grained quartz diorite containing primarily plagioclase with lesser amphibole, orthopyroxene, quartz and biotite (in decreasing order of abundance).  The image below is a thin section (30 microns thick) of the stone using cross-polarized light; the field of view is about one centimeter.


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