[muhth
-er-uhv-purl] 
| 1. | a hard, iridescent substance that forms the inner layer of certain mollusk shells, used for making buttons, beads, etc.; nacre. |
| 2. | of or having the qualities of mother-of-pearl, as being iridescent or pearly: mother-of-pearl buttons. |
| mother-of-pearl
The hard, smooth, pearly layer on the inside of certain seashells, such as abalones and certain oysters. It is used to make buttons and jewelry. Also called nacre. |