How do you value Carbon?

“Diamonds form about 100 miles (161 km) below the earth’s surface, in the molten rock of the earth’s mantle, which provides the right amounts of pressure and heat to transform carbon into diamond. In order for a diamond to be created, carbon must be placed under at least 435,113 pounds per square inch (psi or 30 kilobars) of pressure at a temperature of at least 752 degrees Fahrenheit (400 Celsius).” -   

How Diamonds Work - Bonsor, K