silver 925 and turquoise/ blue stone necklace with crescent

necklace was purchased in posh jewelry boutique in Rome Italy years ago.stamped 925 on clasp. crescent seems like it’s made of some kind of shell or bone. not plastic. there is a little chip or dip on the back of left side edge of crescent not sure if it’s part of the natural surface. please look close at pics smoke free home.