The Granite bedrock in central Minnesota was formed during the Penokean Orogeny, a mountain building event that occurred about 1.9 billion years ago.  This event was responsible for much of the important geological bedrock formations in Minnesota, including the formation of the Animikie Basin that produced most of Minnesota's iron mines and the folding of the rocks in the Thomson Formation.
     The bedrock between St. Cloud and Cold Spring is near the surface and a number of active quarries mine the rock for commercial purposes.  Unlike the iron mines of The Range, these companies sell their products directly to consumers so information is easier to find on the internet (example the "Stone University" of Cold Spring Granite.  Even though the rocks of this area are called granites by many people some of the rocks do not have enough quartz to be granites so they are called syenite.
     This is a photo of the Cold Spring Granite Company on Highway 23 in Cold Spring.  It is a large operation with large blocks of stone in this yard and other yards on the way to St. Cloud.  While not visible in the photograph many of the samples here were not granite indicating that they also quarry stone from other areas.
     The photos below are of syenite with large grains of plagioclase and feldspar but not quartz as identified by Dr. Mahr.  They are in a road cut for Highway 23 just across the river from the Cold Spring Granite Company.
     This is a photo of granite on the river across from the Cold Spring Granite Company.  Quartz grains are visible in this outcrop and the color is much more red than the syenite rocks in the road cut above.  This outcrop is only about 30 yards from the syenite emphasizing the variability of geologic formations only a short distance away.
     The photo at the right is of the Rockville Granite Quarry in Rockville, about halfway between Cold Spring and St. Cloud.  The granite from quarries like these form important building materials, like in the Cathedral of St. Paul, as well as the familiar grave markers.
     The photos of the rocks below stand as gate posts  for the entrance to the quarry.  They stand about four feet square and six feet high.  The large crystals in the rock require slow cooling, deep underground and distinguish this rock from rhyolite that has very fine grain formed when similar material cools rapidly.
     There are additional active quarries on the way to St. Cloud as well as a new building for a company called Capitol Granite that is displaying rock for sale as counter tops and other building materials.

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