Onyx most commonly refers to a variety of chalcedony that is dyed black. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands. Agate has curved bands and onyx has parallel bands. Onyx is referred to as a grounding stone in the metaphysical world.
Each piece is similar, though no item at Crystal Joys is exactly the same as every item uses a unique stone that is non-fabricated. Every item at Crystal Joys is truly "one of a kind". Slight variations in color, size and bead shape exist.