Hello, Francesco,

     As a cowry and cone collector, I've come across quite a few 'doctored'
shells and have learned some ways to figure out the authenticity of shell
features.  I hope you will find these methods useful:

- Painted shells - The painting techniques used to 'restore' dead or
otherwise poorly patterned shells is getting increasingly sophisticated and
professional.  One method I was quite impressed with is the layering of
paint and clear or translucent resin to produce depth in patterns, much like
you see in genuine cowry shells.  A magnifying loupe is useful in detecting
unnatural looking brushstrokes or paint dabbling, but if you have a way of
making a high resolution scan of the shell, you should be able to readily
identify manipulated patterns, bubbles, or other problems.  I have used the
scanner method to identify faked shells I have received in the mail and had
them returned for refund.

- Tapping - light tapping of a highly glossy shell surface such as that of a
cowry shell against your front teeth can expose a resin overcoat.  A genuine
shell surface should give a crisp tap, while a resin-coated one might feel
dull.

- Look for continuity in ridges and growth lines - Cones and voultes are
very often filed, and sometimes the workmanship is such that it is nearly
impossible to tell whether filing has been done or not, especially if the
lip is very sharp.  One way to check is to look for the growth lines along
the lip.  The lines should be continuous from the anterior to the posterior
of the lip.  They should not terminate abruptly part way.

- Layers - In species where a mantle covers over the shell and shell
material is laid down over time, a layering effect occurs.  These layers are
not apparent in a perfect shell, as the upper ones obscure the lower ones.
However, if any cutting into the shell has occurred, you can see the
layering.  As a recent example, I obtained what looked like an exceptional
Cypraea mauritiana with a corrugated (scalloped) base. I have read accounts
from very reputable shell dealers that they have seen live animals with such
a base, so I decided to purchase the shell.  Later, upon inspection in
bright sunshine, I saw the telltale layering I referred to above.  With
further inspection, it was also clear that some of the corrugations were too
finely and sharply cut to be natural.  The polishing done on the surface was
perfect and it didn't even appear that any kind of coating was used.

- Chemical test - Solvents, such as acetone, can be dabbed on a suspected
spot to detect resins, which would dissolve or become cloudy.

- Baked shells - Sometimes it's more than obvious.  For more carefully done
work, look under a magnifier for microcracks and nacre bubbles.

- Sun-bleaching - For glossier shells, sometimes you'll get nacre bubbling
and a dulling of the finish.  Also, carefully look within the aperture of a
shell to see if there is darker, inconsistent color further inside.

- Black light - I've never used this myself, but it makes sense that any
resin or filler used on a shell should show up as a visual  inconsistency in
the shell.

- Too perfect - Truly Gem shells are very rare if one follows the HSN
grading standards in a strict manner.  It's hard enough to get cowries in
true Gem quality, and I really do not believe in Gem Murexes.  Anyways, if a
shell looks too perfect and has too exceptional a feature (size, appendage,
coloration, pattern, etc.), it's time to be cautious.  Also, if certain
parts of a shell look much too perfect to suit the overall quality of the
shell, there's a good possibility of manipulation.

     This is just my two cents on the subject.  I'm sure we can all learn
plenty more from others.

Best regards and aloha,
Dave Lum


>From: Francesco Guarracino <[log in to unmask]>
>Reply-To: Conchologists List <[log in to unmask]>
>To: [log in to unmask]
>Subject: fake shells
>Date: Sat, 25 Dec 2004 18:14:56 -0500
>
>Dear friends,
>
>All we know that quite a lot of “enhanced” shells (mostly cowries and
>conidae) are on the market or in private collections of cheated
>collectors: painted, coated, baked, repaired, polished shells, and so
on;
>e.g., recently somebody talked about cypraea aurantium treated with acid
>and then polished; some years ago even Raybaudi was wrong in considering
>the specimens of the so-called cypraea lobettiana.
>My question is: how do you detect a fake shell? How can you discover if
a
>shell was baked, or discoloured under the sun to make it an albino? How
>can you find out the result of Shell Doctors’ art? It would be very
>interesting to know more about methods of discovering frauds: any
>suggestion and/or opinion?
>
>All the best
>Francesco Guarracino
>Roma - Italy
>
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