Black Onyx is used to ground oneself, for protection and self control - can also be used as a shield against negative energy. Each necklace is completely unique and simply beautiful - semi precious stones surrounded by a Japanese micro macramé thread. One main stone with tiny stones scattered along the string. Okay to wear in fresh water, do not wear in salt or chlorine water. Each necklace is unique and one of a kind, hand made by artisans in Kashmir and Rajasthan. 21.25" long.