Fire Agate 'AA' Grade Cabochon Fire Agate is a form of Chalcedony found only in Mexico and the Southwestern USA, the schiller effect with them is caused by the alternating layers of silica and iron oxide which diffract and allow light to pass and form interference of colours known as 'fire'. It measures approx. 1.2 cms x 1.0 cms x 0.5 cms at the widest points. A dramatic piece for a very reasonable price. Check out my other items ! Be sure to add me to your favourites list !Please remember if you are making multiple purchases to request an invoice before you pay so I can reduce the postage/shipping costs for you.