opal agate

opal agate

[′ō·pəl ′ag·ət]
(petrology)
A variety of banded opal that displays different shades of color, is agatelike in structure, and consists of alternating layers of opal and chalcedony.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.