anthracite which has about 90% C
Amorphous carbon is actually made up of tiny crystal-like bits of graphite with varying amounts of other elements, which are considered impurities.
For example, the coal industry divides coal up into various grades depending on the amount of carbon in the coal and the amount of impurities.
The highest grade, anthracite, contains about 90 percent carbon.
Lower grades include bituminous coal , which is 76 percent to 90 percent carbon, subbituminous coal, with 60 percent to 80 percent, and lignite, with 55 percent to 73 percent.