Carbonado in the pores that are common in carbonados, they may have been introduced after carbonado formation. Inclusions of other minerals, rare or nearly absent in the Earth's crust, are found at least partly incorporated in diamond, not just in pores: among such other minerals are those with compositions of Si, SiC, and Fe‑Ni. No distinctive high-pressure minerals, including the hexagonal carbon polymorph, lonsdaleite, have been found as inclusions in carbonados, although such inclusions might be expected if carbonados formed by meteorite impact. Isotope studies have yielded further clues to carbonado origin. The carbon isotope value is very low (little carbon‑13
Rock Hawk Rock Hawk Rock Hawk Effigy Mound is an archaeological site in Putnam County, Georgia, United States. () It consists of thousands of pieces of quartzite laid in the shape of a large bird. Although it is most often referred to as a hawk, scholars do not know exactly what type of bird the original builders intended to portray. Only two such effigy mounds have been found east of the Mississippi River. The other, known as Rock Eagle, is also located in Putnam County, approximately thirteen miles to the northwest. () The physical condition of Rock Hawk is far below that