This winter, our shop finished several more of the rare green stromatolite from the Green River Formation of Wyoming. The green color comes from geothermal fluids forced into the stroms & the minerals they carry left behind. An unusual find indeed. The color most likely is iron with other minerals, perhaps even copper included. This mirror polished colony half is a horizontal section or cut through a small complete colony. MIrror polished surface is approx. 4 3/4 x 5 inches & is approx 1 inch thick at its max. Best of all is that this specimen has a reverse side that displays a naturally weathered surface. Sweetwater Basin, Wyoming. Middle Eocene. Green River Formation. Weighs 1 lb. This is a fine display specimen. We want you to have confidence in our specimens. Please feel free to request more pictures, information or details! Please remember that we are always willing to combine listings to save on shipping. More questions - please ask. PLEASE NOTE THAT WE DO OUR BEST TO COMBINE SHIPPING ON MULTI ITEM ORDERS!! WE SHIP ONLY TO THE UNITED STATES., CANADA, & U.S. TERRITORIES. FORGEIN CUSTOMERS WITH INTERESTS SHOULD CONTACT US PRIOR TO PURCHASES. stromatolite, Rare Green Color, Hydrothermal Solution, Middle Eocene, River Fm., Mirror Polish/Natural Side, Complete Colony Half