Marble is rich in crystals and comes in a variety of colors including white, cream, charcoal, green, and pink. The color of any marble depends on the type of stone it is, how it was formed, and where it is from. For example, black marble from Africa is called onyx, and blue marble from Italy is called travertine. The most common types of marble are white marble which makes up 90% of all marble used in construction, brown marble which makes up 5% of all marble, and colored or variegated marbles which make up 5% of all marble. There are three main types of white marble: California white marble, Colorado white marble, and Australian white marble. California white marble is found in coastal California and consists of calcium carbonate with small amounts of magnesium carbonate and sodium carbonate. It is the most expensive type of marble because it is so dense and heavy that few buildings are made from this material. Colorado white marble is found in the Rocky Mountain region of Colorado and Utah and consists of almost pure calcium carbonate. Australian white marble is found in eastern Australia and includes varieties such as quartzite, shale, and sandstone that contain varying amounts of iron oxide.