| The core of those structures is made of a protein called conchiolin, a common component of many mollusk shells. |
|
| Pearls which have been known to be 200 years old have turned black because of the decay of the conchiolin. |
|
| This combination of calcium carbonate and conchiolin is called nacre or mother-of-pearl. |
|
| Moreover, the chambers were divided by a system of numerous intracameral layers of conchiolin and protein. |
|
| Tropical shells tend to have higher metabolic and growth rates with higher conchiolin content. |
|
| It is probable that other skeletal proteins in invertebrates, such as the spongin of sponges and the conchiolin of mollusks, are also tanned proteins allied to sclerotin. |
|
