Lovely Amethyst & Lava Rock Stretchy Bracelet. Lava rock is 8 mm and can be used as a Diffuser for Essential Oils. 8 mm Polished Amethyst is a stone that is considered protective, healing and of spiritual wisdom. Violet is the Color most associated with Archangel Zakiel. He is the Angel of Freedom, Mercy and Benevolence. Fits wrist sizes 5.5-7 inches.