Black onyx is a member of the Chalcedony family of quartz, and has a hardness of 6.5 to 7, its colour black and white, but it is the black part which gave its name "black onyx". It is found in Brazil, Mexico, Argentina, Madagascar and India, and its name is derived from Greek "onux", which means claw or fingernail. Onyx is the black variety of agate of volcanic origin. In India, it is renowned for fighting evil forces. Like all black stones, it absorbs negativity, whether from a place or from thoughts emitted and received around it. It acts as shield for its owner. It is a good stone for dreamers, as it grounds and connects to the earth. It is a precious help for relieving cardiac pains and buzzing ears. It is not advised for pregnant women, and wearing it continuously can generate sadness, melancholy, inertia, moroseness, and cause nightmares. In combination with another stone, it can be an element of balance.