Shells--a miracle on earth

At previously time, I only contact with one kind of product. Those are marble mosaic. At the process of learning marble mosaic, I am attracted by marble mosaic deeply. The texture of marble is developed by our designers incisively and vividly. The more in-depth study, the more marveled by the magic of nature. It is the nature that makes such magic.
Today, I have seen another miracle that nature give us-- shells. Shell is not strange to everyone. But are you familiar with such shells?

Yes, these marvellous artwork are made of shells. I searched shells on internet because I think that my awareness of shell is so shallow. 
I found that shells are coat film of mollusks living in the water. they have a special kind of gland cell and their discharge can be formed calcifications to protect soft part of the body. These calcifications are called the shells. Some have the iridescent sheen like pearl, which is used for jewelry, necklace, fashion jewelry. In all kinds of shells, northern Australia Torres Strait area of pearl oysters (pinctada maxina), Manila in the Philippines, myanmar of the shell and the west Indies geoduck are the best.

Pearl is an ancient organic gemstones, produced in the pearl shellfish and pearlescent shellfish mollusks and generated by endocrine function. They are composed of a set of small aragonite crystals. According to the geology and archaeology research, the pearl come into existence two hundred million years ago.
http://www.aliexpress.com/store/product/2015-new-design-mother-of-pearl-tile-free-shipping-mosaic-tile-backspalsh-shell-mosaic-tile/404850_32403778206.html