She sells sea-shells by the seashore

I thought I'd answer a question posed by Barbie's Ex (Ken???) That was a really good question but it is really 2 questions so I'll answer them both and ask a trivia one too.

For those who are too lazy to look up the question here it is 'hey Mr c how are shells made? Like the big ones you put your ear on to hear the wind whistling through your ears?'

Well firstly you start off with an organism which is about the size of a pin head- (some are bigger most are that small) Its blood has a very high concentration of Calcium and Carbonate. At the mantle of the animal it secretes it which depending on the mantle's shape a protective layer. I'll use the conch shell as the example. So it surrounds itself with the mantle or Lip as the only exposed area. The calcium calbonate keeps getting deposited as the animal gets bigger. We aren't really sure if this is a excretetion over time or if the animal can control it. All we know is that it is such a example of a higher system that must have delevoped over millions of years :) Just thought I'd give an example of what the mantle is- if you look at a snail the mantle is the part of the snail you can see when it is in its shell. Clam shells the mantle is the coloured section- different shape mantle different shell design. So the shells keep exanding as the animal's size does.
Now Seashells do not really make any sound of their own. Inside they have many hard curved surfaces, which are good reflectors for sound. So any sound waves that get inside are jumbled up by all kinds of echoes. When you hold the shell up to your ear, you hear the noise of all those jumbled-up echoes. That does sound much like the noise of ocean waves beating against a shore.
If you have a seashell with a big cavity inside, try it out again at home next to your ear. Unless you get in a very, very quiet place, it will keep roaring as if it had brought some of the ocean with it. But you will hear nothing in space :) because you will be dead.
There is a fascinating shell that I thought i might point out. Spirula has a chambered shell of Nautilus. Each chamber is connected to the body by a tube called the siphumcle. The chambers are filed with a special liquid and gas mixture. Spirula can float or sink by changing the pressure on this mixture. So this thing literally controls its depth by pressure in the chambers in the shell.
Trivia Question:
What shell based/derived product/food sold the most in the year 2004? (yes the thing is a food.
Any other sea questions you'd like me to answer?