Graphite

definition: 
A grey crystalline allotropic form of carbon which occurs as a mineral in some rocks and can be made from coke. It is used as a solid lubricant, in pencils, and as a moderator in nuclear reactors
sentence: 
One possibility of this sort of manipulation could turn carbon into either graphite or diamond.
difficulty: 
medium
toefl frequency: 
1
toefl classification: