Carbonado typical gem diamonds. Lead isotope analyses have been interpreted as documenting crystallization of carbonados about 3 billion years ago. The carbonados are found in younger sedimentary rocks. Mineral grains included within diamonds have been studied extensively for clues to diamond origin. Some typical diamonds contain inclusions of common mantle minerals such as pyrope and forsterite, but such mantle minerals have not been observed in carbonado. In contrast, some carbonados do contain inclusions of minerals characteristic of the Earth's crust: these inclusions do not necessarily establish formation of the diamonds in the crust, however, because while these obvious crystal inclusions occur
Rock Eagle Rock Eagle Rock Eagle Effigy Mound is an archaeological site in Putnam County, Georgia, U.S. estimated to have been constructed c. 1000 BC to AD 1000 (1,000 to 3,000 years ago). The earthwork was built up of thousands of pieces of quartzite laid in the mounded shape of a large bird (102 ft long from head to tail, and 120 ft wide from wing tip to wing tip). Although it is most often referred to as an eagle, scholars do not know exactly what type of bird the original builders intended to portray. It is listed on the National Register