Fire agates were formed when hot water, saturated with silica and iron oxide, filled cracks and cavities in the surrounding rock and solidified into chalcedony layered with crystallized iron oxide . The vibrant iridescent rainbow colors found within fire agates are created by the Schiller effect, which is also found in mother-of-pearl. The brown color and iridescence of fire agates is due to inclusions of the iron oxides goethite or limonite. Fire Agate: Mexico 65 x 21 x 14 mm about 5.4 grams the piece for sale is what you see in photos! please be careful with the description and measures Standard shipping ( 2-7 days for Italy ) ( 10-20 days for Europe ) ( 15-40 days for rest of the world ) if you want fast shipping, please contact me immediately after the auction win