Chemical element chemical bonds, they form chemical compounds. Only a minority of elements are found uncombined as relatively pure minerals. Among the more common of such native elements are copper, silver, gold, carbon (as coal, graphite, or diamonds), and sulfur. All but a few of the most inert elements, such as noble gases and noble metals, are usually found on Earth in chemically combined form, as chemical compounds. While about 32 of the chemical elements occur on Earth in native uncombined forms, most of these occur as mixtures. For example, atmospheric air is primarily a mixture of nitrogen, oxygen, and argon, and
Blue diamond secondary hues that can be found in blue diamonds. Blue diamonds are considered most beautiful and valuable when there is no secondary color present but rather are a pure blue color. However, a pure blue diamond of light color may be considered less valuable than a green-blue or gray-blue diamond whose color is more vivid. The characteristic of color is very complex in blue diamonds for this reason. Most pure blue diamonds are Type IIb, meaning they contain either very few or a complete lack of nitrogen impurities. Type Ia blue stones contain a secondary hue and get their color