Nacre is found in certain ancient lineages of bivalves, gastropods and cephalopods. However, the inner-shell layer in the great majority of shelled mollusks is porcellaneous and non-nacreous, frequently resulting in a non-iridescent shine like that of a porcelain plate or, in some species, presenting non-nacreous iridescent effects such as 'flame structure' (e.g. conch pearl)

Pearls and the inside layer of pearl oyster shells and freshwater pearl mussel shells are made of nacre. Many other families of mollusks also have an inner shell layer which is nacreous, including marine gastropods such as the Haliotidae, the Trochidae and the Turbinidae.

A few of our Mother of Pearls Hand Made in Bethlehem:

   

Following are very interesting readings on Jerusalem and Bethlehem:

http://en.wikipedia.org/wiki/Jerusalem

http://en.wikipedia.org/wiki/Bethlehem#Mother-of-Pearl_carving