Black onyx is the birthstone for Leos (for those born from July 23 - August 22)and the anniversary gemstone for the 10th year of marriage.
Onyx is said to be a protective stone and may be carried or worn for courage. It is also said to provide support in difficult times and to center your energy in times of mental or physical stress. It also offers the gift of wise decisions.
Contemporary authors say the onyx brings increased vigor, strength, stamina, and self control. It alleviates worry, tension, and nervousness and eliminates confusion and nightmares.
All in all, the black onyx is a good stone to have nearby!