SAUK RAPIDS, Minn. -- For Lyndon Johnson, treasures can be found anywhere -- one just has to train his or her eye. "I know when to look and where, and where to look when," Johnson said with a smile.

Mineral deposits can create markings that look like forests or mountains, and experts say each stone is distinctive. By Jill Newman When Tarun Adlakha displays a dendritic agate, with its finely ...