Onyx is associated with beating time, and thus it is used for rejuvenative treatments, in hopes of long life.
Zodiac: taurus, scorpio, capricorn.
Read more about this crystal: Onyx
Running lukewarm soapy water is the best for cleaning this stone. Bury underground or stick into the soil (flower pot) couple of times per year for one night - it restores stones beauty. Likes sun and moon, but as any other crystal doesn't tolerate household chemicals and perfumes.