Most of us know the shell just can be picked up from sea side, know that the shell is the outer surface of the mollusk, but mostly do not know the details of it.
It is an interest thing to search and learn it.
The shell is formed by calcium excreted by the mollusk to protect itself, the calcium thing is the shell that we called.
The main component of the shell is calcium carbonate and little chitin.
Normally it has three layers, the outside layer is the horn in black and brown, actually the skin of the shell which is thin and clear but protecting the carbonic acid from eroding.
The middle layer is the thick prism layer called lamella which is formed by the calcite excreted from the membrane edge.
These two layers can expand the shell without increasing thickness.
The inner layer is called the pearl layer of the mollusk.
This layer is the most important and functional layer of the mollusk, to become thick following the growth of the mollusk, formed by the argentite excreted from the whole membrane surface with beautiful luster.
Besides the calcium, the shell also has other component like the shell protein.
Protein is the vital matter of the mollusk.
It is a continual secretion and folded up layer by layer which make the shell hard and hard, some even bring the luster to the shell.
The mollusk enlarges itself by excreting from the edge of it.
Because of the periodicity of continuity of the growth, the shell has very beautiful color line on the surface.
The shell of the mollusk is not only the protection but also the decoration thousands of years ago.
The Europe nobles used the shell from deep sea as their luxury symbol because it has the charming and magic color and luster which is similar but different from the pearl.
Later in China people began to abrade and decorate it as the buttons in some high grade clothes.
It is also the favor material for modern designers.
The natural pattern and color of the shell is fit for the most consumers with some individual jewelry.
The shell also becomes the favor of those collector, the elegant and natural feature is fit for their aspiration.
But to protect the ocean resource, many countries regulate to limit or prohibit the collection aside beach or gaining the shells in deep sea or else the punishment will be on you.