1) Nacre 
Conchiolin (sometimes referred to as conchin) are complex proteins which are secreted by a mollusc`s outer epithelium (the mantle). These proteins are part of a matrix of organic macromolecules, mainly proteins and polysaccharides, that assembled together form the microenvironment where crystals nucleate and grow. This organic matrix also holds a....
(from the article `jewelry`) ...colours, of which the most sought after are rose red to red. The best coral comes from the Mediterranean Sea, particularly off the coasts of ...
conchiolin A nitrogenous substance that is the organic basis of many molluscan shells.
a fibrous protein that forms the iridescent inner layer, as mother-of-pearl, in the shells of mollusks.