Lake Superior Agates are red, yellow and orange iron stained banded agate. Deposited by Glaciers along the shores of lake Superior and the adjoining states of Minnesota, Wisconsin, and Michigan. They can also be found in parts of Northern Iowa and Thunder Bay, Canada. In 1969 the Lake Superior agate was designated the state stone of Minnesota. Lake Superior agates are generally small agate pebbles and nodules ground down by Glacial and other natural erosion.