Out of the Attic: Mississippi clam shells were basis for pearl button industry Julie Martineau Des Moines County Historical Society Catalog number 73.82 is described as a clam shell from the Mississippi River, given to us by a Mrs. Carl Myers of Mediapolis. The object its self is unassuming, and indeed, common enough in this area. In fact, they are so common they were the basis for an entire industry. The remnants of the Mississippi Pearl Button industry still can be found in old concrete and along the river front fairly regularly. Shells with holes punched in them were used to reinforce and fill concrete aggregate and were thrown in the river for many a year.