pearl identification

[water]

Hi everybody  <img src="images/smiley/smile.gif" alt="" border="0" />. My first time on this forum. I would need your comments on the attached photo. Those, mostly dark purple nacreous pearls, ranging from approx. 2mm to 6mm are presented as coming from the Modiolus philippinarum shell. As anybody ever come accross natural pearls from this shell ?
Many thanks

Water
<a href="http://www.badongo.com/pic/2974260" target="_blank"><img src="http://www.badongo.com/t/250/2974260.jpg" alt="http://www.badongo.com/t/250/2974260.jpg" style="border:0" /></a>

[paul monfils]

Virtually any bivalve can produce a pearl. It is the way bivalves deal with irritating particles that get trapped in their soft parts and cannot be flushed out.  Someone in my area recently found a large purple pearl in a Venus Clam, Mercenaria mercenaria. However, many such pearls have no gem value because the outer surface of the pearl resembles the inner surface of the bivalve shell. A bivalve with a chalky white interior may coat an irritating sand grain and produce a pearl, but the pearl will be chalky white and not much to look at. The interior of Modiolus philippinarum is semi-nacreous and dark colored, so the pictured pearls may well have come from that species, but there is no way of knowing for sure.  <span class="petit">--Last edited by Paul Monfils on 2008-02-23 08:12:14 --</span>