How many years does it take for carbon to form into a diamond?

How long does it take a diamond to form?|||Millions of years as far as natural diamonds are concerned. Diamonds are a crystaline form of carbon. Carbon itself is soluable in liquid iron just as sugar dissolves in water. Both water and liquid iron can hold a certain amount of dissolved material. When the solution saturates, crystals begin to form. Small industrial diamonds can be artificially manufactured very quickly, but they are grey to black in color. Gemstones need precise amounts of temperature and pressure to allow quality diamonds to form. The Russians have nearly perfected a technique to make artificial gemstone diamonds.