Mother-of-Pearl: A true treasure of the deep South Pacific waters. It is the smooth, lustrous, and iridescent lining in the shells of the pearl oyster. Penshell: This large fan shaped shell is indigenous to the Philippine waters. The inside of this shell is smooth and shiny and varies in color from black and dark brown to light brown and amber. The shells are crafted by native Philippine artisans for jewelry, and resembles marble in appearance and durability.