It is thought to ensure a variety of positive effects, such as invisibility, good luck, protection from malevolent magic, rebirth after death, and romantic success.
[1] ...I got a black cat bone, I got a mojo too, I got the John the Conqueror root, I'm gonna mess with you...
[2] The use of the black cat bone to ensure invisibility, specifically as an aid to people, is comparable to the European Hand of Glory.
[3] After a black cat is caught, it is almost universally boiled alive in a pot of water at midnight, so that its bones may be more easily looked over by the practitioner.
One method of obtaining a black cat bone, described in Zora Neale Hurston's Mules and Men, involves a period of fasting before the actual catching of the animal.