>There is another way to find out if your shell is fossilized or not.
>Due to the recristallisation the shell becomes less translucent with
>'aging'. Just hold a strong torch/lamp behind the shell. If it is
>normally translucent it is a 'fresh' dead specimen. Within a couple
>of thousand years they are not translucent at all anymore so in a
>fossilized shell your torch will not shine trough anymore.

That entirely depends on the fossil's burial history as well as the
fossil's original composition. I have plenty of 25 million-year-old
and older (Oligocene) Lentipecten scallops which are as translucent
as the day they died.

Most mollusc shells are almopst entirely aragonitic; this MAY alter
to calcite with age. Originally-calcitic forms (eg oysters, mytilids,
anomiids, psctinids, spondylids, limids, epitoniids and Pteropurpura)
don't normally recrystallize and are more likely to remain
translucent.

Also I have seen how Recent (aragonitic) micros from my canyon
dredgings turn opaque white some time after death; living or
fresh-dead ones are transparently glassy (marginellids,
scissurellids, muricids). I am sure some of the live-caught ones, 5
years after their deaths, are turning cloudy. These have been kept
entirely in the dark, in sodaglass vials.
--
Andrew Grebneff
165 Evans St, Dunedin, New Zealand
64 (3) 473-8863
<[log in to unmask]>
Fossil preparator
Seashell, Macintosh & VW/Toyota van nut
I want your sinistral gastropods!