During the last ice age, some 12,000 years ago, glaciers deposited granite rock on what would become Iowa fields. Typically the granite is well rounded and range from a few inches in size to several feet. Some house-size boulders can be found scattered around the state. A road trip in farming areas will usually yield sights of granite rock piles on the edge of farm fields. These piles represent the land owners collection of stones harvested over time as the fields are worked mechanically. With some analysis these granite specimens can be identified as originating from Minnesota or further north in Canada.
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