Limestone is one of the main types of sedimentary rocks.
   Sedimentary rocks are those which result from deposition of minerals by water or wind, and limestone is defined as a bedded sediment composed primarily of calcium carbonate (CaCO3).
   Limestones are indicative of a deep-water environments, and many types of fossils are found in them.  It sometimes forms massive cliffs, like the Mississippian age Red Wall limestone seen in the Grand Canyon of Arizona.
   When limestone is modified by heat and pressure, it becomes the stone we call marble.
   Roosevelt Dam in the Salt River Canyon east of Phoenix is constructed from blocks of limestone, which was deposited in a vast ocean during Precambrian time.


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