Rare Girvanella Form of Precambrian Stromatolites from Utah

Description: This particular specimen exhibits a rare structure for stromatolites, the so-called Girvanella-form comprising irregular, unsymmetrical spherical nodules. Note the cross section of the nodules contained within the specimen. Such forms are more commonly found in Cambrian and younger stromatolite, when bacterial colonies were subject to predation. This stromatolitic carbonate has been hand-polished to a mirror finish on one side to bring out the details in striking contrast.