Nickel is silver white in color when the metal is in its natural form. Nickel compounds express in blue, green and yellow.
Nickel is a silver white crystalline metal and is the 22nd most abundant element on Earth. It is found in meteors or with other elements in ore groups. Nickel is found in laterites, which are oxide or silicate ores from in tropical areas. Nickel is also found in sulfides, which contain a small amount of nickel along with other metals such as copper and cobalt from cooler regions. The process of turning nickel oxides into pure nickel metal through purification developed in the late 19th century. In its natural state, nickel is magnetic and conducts electricity, but does not react quickly to oxygen.
Compounds and alloys of nickel are often blue or green in color, particularly when the compound is hydrated. Nickel oxide powder is used to make green glass. The same powder turns yellow when heated. Nickel oxide has occurred naturally in diamonds, where its presence produced a greenish yellow tint within the stone. Gemologists at the Gemological Institute of America, an organization that specializes in the classification and rating of gems, states that while nickel may be present within a diamond, a concentration high enough to color the stone is unusual.