Pencils contain graphite & clay, plus some wax (the wax is added for lubrication). The responses provided above are correct, but the information in the chart reproduced below might be of interest to you.
[The chart is from :
Sousa MC, Buchanan JW. "Observational models of graphite pencils". Computer Graphics Forum 19.1 (2000): 27-49. P. 30. … Read more
