Hi Olivier
Just a note.
Though I don't remember too much on the subject...

The are multiple sources from which colour is expressed in shells.
Some are true pigments, others are mineral based, and are implemented into the
shell in different ways, etc.

I believe there was an article on it a few years back in the American
Conchologist, ... but it may have only been at a show or convention.

Seems like the article / exhibit listed three variants, each with its own
technical term.

Leslie

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Dear list,
As I was observing some violet or purple shells, I wondered which was the
molecule responsible for this colour.
I thought of the family of the anthocyanes, which are red in an acid
environment, and become purple when the pH runs to more basic values.
But, as I'm not a chemist, it may be that I'm mistaken.
If the anthocyanes exist in plants, do they exist underwater ?
What are the names of the other UW pigments ?
Black for melanin, yes, but then ?
Quid for the orange/yellow, quid for the red ? What is at the origin of the non
nacreous green appearance (as in a Turbo marmoratus,  or in a Smaragdia
viridis?)

Any idea ?
Cheers !
Olivier
Caro