Marble and Travertine is formed by the recrystallization of limestone and the like under high temperature and pressure. This could take thousands or millions of years. Fossils also come out of these rocks. Marble contains 56% calcium oxide (CaO) and 44% carbon dioxide (CO2). The various colors of the marble are due to the inclusion of a small amount of iron or other metal oxides in its composition. Among the minerals that give color to the marble are talc, mica, graphite, iron oxides, pyrite and quartz.