Material properties of diamond these are known as ballas and are important to industry as they lack the cleavage planes of single-crystal diamond. Carbonado is a similar opaque microcrystalline form which occurs in shapeless masses. Like ballas diamond, carbonado lacks cleavage planes and its specific gravity varies widely from 2.9 to 3.5. Bort diamonds, found in Brazil, Venezuela, and Guyana, are the most common type of industrial-grade diamond. They are also polycrystalline and often poorly crystallized; they are translucent and cleave easily. Because of its great hardness and strong molecular bonding, a cut diamond's facets and facet edges appear the flattest and sharpest. A
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