Onyx is available in a wide range of qualities, not all of which are therapeutic. Gemisphere sells only the highest-grade Onyx spheres, which are a deep, consistent black and precisely cut for maximum therapeutic effectiveness. Therapeutic Quality Onyx Therapeutic Onyx spheres are a deep, consistent black, and their shape and drill holes are precise and even. Unlike most other gems, Onyx’s therapeutic power is enhanced by dye. Indeed, black Onyx is derived by dyeing Gray Onyx black.