Mother of pearl is the iridescent internal layer of mollusk shells and is composed of nacre, the same material as pearls. Though technically not a gemstone, mother of pearl is used in all types of jewelry from watch faces to fashion jewelry.
The lovely appearance of mother of pearl is valued for its opacity and iridescence. Mother of pearl is generally whitish or off-white, but can occur naturally in pink, purple, green or gold. Different mollusks produce different shell colors. This material may also be dyed or bleached to attain a specific color.
Mother of pearl is thought to attract prosperity and luck. A very soft substance, mother of pearl has a Mohs hardness rating of 3.5.