mother-of-pearl
noun [ U ] uk/ˌmʌð.ə.rəvˈpɜːl/ us/ˌmʌð.ɚ.əvˈpɝːl/
珠母层，珍珠母
a smooth, hard substance forming a layer inside the shells of some sea creatures. It is white but also seems to shine with different colours, and is used to make buttons and for decoration.
Synonym: nacre