What's on my conch shell

[Hanaleimom]

My conch shell has some dry flakes over it. I've scrubbed most of it off with a dish pad and water but there are still some in the crevices. What is it? By the way, when dry they look lighter.

 

[pattye]

Hi Cathy, Giving this a bump, since it isn't showing up as a new post. That is interesting, but I have no idea what it is. Bet the other side is really pretty! Hopefully our shell experts will show up tomorrow.

 

[Lagoon Island Pearls]

It's conchiolin. A waterproof resin-like material made from protein and sugar. It forms the outside layer of every mollusk called the periostracum. Some retain it permanently, but in many it breaks away as the shell thickens or becomes dried.

 

[Hanaleimom]

Thank you Pattye and Dave.

Dave, this conchiolin comes in layers right? Does this flaking continue if it's been removed but continues to sit by a sunny window a few hours a day? Does dunking it in water every once in a while help? Thanks in advance.

 

[Hanaleimom]

Ttt.........

 

[Lagoon Island Pearls]

Thank you Pattye and Dave.

Dave, this conchiolin comes in layers right? Does this flaking continue if it's been removed but continues to sit by a sunny window a few hours a day? Does dunking it in water every once in a while help? Thanks in advance.

It's two thin sheets extruded simultaneously by the inner surface of the outer fold of the mantle at the very outer edge of the shell. The main function of it is to create a water tight barrier so new shell can be mineralized in the space created. Interestingly enough, it's turns 180 degrees from the direction it's extruded from. Once the portion of new shell is mineralized, other than protect the shell slightly, it doesn't serve much of a purpose afterwards and in many species falls away while the critter still living.

It contains water, so as it dries it cracks and peels. Re-moistening will probably prolong it from falling away.

My target species is Mytilus californianus (California mussel) which has rich, thick conchiolin in the periostracum. If I set shells indoors to dry, in a few days, I can hear the conchiolin crack and peel from across the room.

 

[Pearl Dreams]

Utterly fascinating! My conch shell has a [very little] bit of conchiolin on it as well, and I always wondered what it was.

 

[GemGeek]

Thanks for a terrific explanation.