Natural Citrine is a quarz crystal (SiO2) that has a varying tome from a ivory yellow to a yellow, smoky yellow and the rare rich amber. This is caused by the addition of iron hydrates at the time of crystalization in the layers of the earth. It has pzyzoeletricity as in all other quartzes it can translate mechanical stimulation into electrical charge and vise-versa. ( More information on this on Kendra Grace's book, "Aromatherapy, Crystals and Vibrational Healing", pg 145.