Black Onyx Sphere 11 3/4pz (332g) 2.5" (or 6cm) diameters The same can be true of any belief which no longer serves one - and they can be as hard to let go of as past relationships. Onyx's value in such situations is that it can help to bring us into contact with our actual realities, and assist us in gradually releasing all that is not in harmony with our present lives.