I think that you slipped some decimal places somewhere. The most common allotrope of carbon, graphite, has a density of 2.26 metric tons per cubic meter. Texas

I think that you slipped some decimal places somewhere. The most common allotrope of carbon, graphite, has a density of 2.26 metric tons per cubic meter. Texas has an area of 695,663 square kilometers. Covering Texas with a 1 meter (~3 foot) layer of graphite would consume 659663 * 1000 * 1000 * 2.6 = 1,715,123,800,000 tons (1.7 trillion tons) of carbon. One billion tons of carbon would make a Texas-covering graphite layer about 0.58 millimeters thick.