Mother of pearl (MOP) is made from the inside of the oyster shells.
MOTS (never seen before here) is cellulose a man made highly volatile material used in knives because of its beauty. I just had to throw out a set of beautiful cell handled steak knives that I found in the cellar as one of the handles stared gassing out so badly it had turned to liquid.
Definitions:
Nacre pronounced /ˈneɪkər/[1] or "NAY-kər", also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer; it is also what makes up pearls. It is very strong, resilient, and iridescent.
Nacre is found in some ancient lineages of bivalve gastropod and cephalopod. The inner layer in the great majority of mollusk shells is porcellaneous, not nacreous, frequently resulting in a non-iridescent shine or less commonly in non-nacreous iridescence such as flame structure (e.g. conch pearl).
Pearls and the inside layer of pearl oyster and freshwater pearl mussel shells are made of nacre. Many other families of mollusk also have a nacreous inner shell layer, including marine gastropods such as the Haliotidae, the Trochidae and the Turbinidae.
A great link to the story on cell.
http://www.oregonknifeclub.org/celluloid_02.html
