Recent research with carbon has amplified knowledge of fullerenes, especially the C₃₆ molecule and nanotubes. Carbon is an important element occurring in a staggering number of compounds, many with extensive industrial uses. Carbon is found in nature in two pure crystalline forms: as diamond, an insulator that is the hardest material known; and as graphite, a soft, electrically conducting material. Graphite is used in pencil lead and as a lubricant, among other things.