Dear Kay,

in 1960, JA Allen  published an article titled "Manganese deposition on the
shells of living molluscs", Nature, 185: 336-337 that described at least the
black deposits on the tip of the scaphopod Dentalium entale containing
Manganese.
Best regards
Bernd Sahlmann
from Munich


----- Original Message -----
From: "Kay Peterson" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, January 05, 2005 9:27 PM
Subject: Re: Ferruginous layer


> Another question about blackened shells.  Most of my Fulgoraria species,
> from
> Taiwan, as well as my Alcithoe arabica, from Auckland, have seriously
> blackened spires.  I have never seriously tried to remove the black,
> because I don't
> wish to remove the periostracum.  (Also, like cleaning silver, I don't
> wish to
> remove the dark portions, which serve to enhance details of the sculpture.
>
> I note that the A. arabica was found in mud.  Would that give you a clue
> as
> to the nature of the discoloration?  As I said, only the spires are
> blackened.
>
> I have found beaches in Massachusetts where many black shells can be seen.
> The species range from Pecten to Natica---and almost everything else in
> between.  Someone told me that "anaerobic decomposition" had something to
> do with it.
> These shells, unlike my volutes, are black all over.
>
> Ideas?  (As to cause, not necessarily for cleaning---)
>
> Thanks.
>
> Kay
>

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