Randstones are typically Anorthosite, Diabase, Gabbro or Syanitic Gneiss with the occasional peice of Potsdam Sandstone or Iron Ore. The geologic story of these stones is unique to the High Peak Region of the Adirondack Mountains in Upstate New York. The story starts 1.2 billion years ago 18 to 20 miles below the surface of the Earth. Where the Anorthosite of 43 of the 46 Adirondack High Peaks cooled as magma for several hundred million years. The Magma ended up as an assortment of Plagioclase Feldspars (Andesine and Labradorite) with numerous inclusions an reactions. 50 million years ago the Adirondack Dome began to rise, pushing up, what are today’s Adirondack High Peaks to the hights of the Himalayas. During this massive uplift cracks opened up in the Anorthosite allowing magma to fill the voids. These magmas cooled quickly resulting in the Gabbro and Diabase you see in many dikes and lenses in the Anorthosite. On top of the Anorthosites were sedementary sandstones like the potsdam formation and limestone like the chazy group. Millions of years of weathering and erosion worked away at the covering sedementary stone until the Pleistocene Glaciations finished the job, exposing the Anorthosites of the Adirondacks.