Mother of pearl; a thin layer of sediment, similar to boulder opal. A nacre coating produced by mollusks, often used in jewelry. Due to pearl farming mother of pearl is widely available. This also explains the aversion to using it: pearl farming is unnatural and often not environment friendly. The pieces used in this artwork are natural resources. Freshwater mollusks eaten by birds. The uneatable shell is left behind, free to use by people like me. [Daily Abstraction 218100501, Painting available].