- noun a mineral form of carbon occurring naturally as crystals or as a soft black deposit
- The most common crystalline form of carbon, found in pencils and interstellar gas clouds
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- noun a form of carbon used in making brushes for motors and generators and as a lubricant
- An allotropic form of the chemical element carbon. It is a soft black solid which conducts heat and electricity well. Its applications include its use as electrodes, in brushes, in electroplating, as a coating for CRTs, as a moderator in nuclear reactors, and as a lubricant.