Downing, Paul B., Ph.D. <br/><br/>
Opal identification and value 
/ by Paul B. Downing 
 - Tallahassee, FL  : Majestic Press  , 1992. 
 - x, 210 p.  : ill. (some col.)  ; 24 cm. 
<br/><br/>Includes bibliographical references (p. [195]-200) and index. 
<br/><br/><label>ISBN: </label>9780962531125 
<br/><br/><label>LCCN: </label>95230997 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Opals
<br/><br/><label>Dewey Class. No.: </label>553.8 DOW