Also known as gold mother-of-pearl, this is the iridescent inner layer of nacre found only in a certain species of freshwater pearl mussels (which are actually clams, not mussels) in the family Unionideae, or Unio for short. The outer edges of the shell have the darkest, most vivid color, which is why it earned the name “gold-lip.” Endemic to freshwater rivers, lakes, ponds, and streams in a number of eastern states, this particular mussel produces an inner protective nacre that is distinctively gold in color, rather than typical mother-of-pearl, which has a bluish-white cast. Other mussels may have a yellowish, purplish, or blue-green nacre.
Gold-lip pearl has been used for centuries in the production of buttons, but because of its relative scarcity, these would most often find their way onto only the most expensive apparel. It has also long been an upscale material for jewelry and inlays in fine acoustic instruments, such as guitars and mandolins. At present, it is an endangered species because of pollution, extended periods of drought, and over-collecting. Most luthiers and some musical instrument manufacturers made large purchases, as this material became periodically available in the past. So, at this time, there are adequate supplies for use in high-end instruments, including some recent PRS Private Stock guitars, in which the gold-lip pearl is inlaid with a fine outline of real gold (talk about an intricate fit!).