Noah Webster's Dictionary (n.) The hard pearly internal layer of several kinds of shells, esp. of pearl oysters, river mussels, and the abalone shells; nacre. See Pearl.

Multi-Version Concordance Mother-of-pearl (1 Occurrence) Esther 1:6 white linen, white cotton, and blue, fastened with cords of fine linen and purple on rings of silver, and pillars of marble, couches of gold, and of silver, on a pavement of smaragdus, and white marble, and mother-of-pearl, and black marble -- (YLT NAS RSV NIV)