Merriam-Webster Collegiate Dictionary - agate

 noun  Usage: often attributive  Etymology: Middle French, from Latin achates, from Greek achates  Date: 1570  1. a fine-grained variegated chalcedony having its colors arranged in stripes, blended in clouds, or showing mosslike forms  2. something made of or fitted with ~: as  a. a drawplate used by gold-wire drawers  b. a playing marble of ~  3.  a. a size of type approximately 5 1/2 point  b. condensed information (as advertisements or box scores) set especially in ~ type