Which allotrope of carbon is widely used as a lubricant and in pencils?

Explanation

Graphite has a layered structure where sheets of carbon atoms stack loosely on top of each other. These layers slide easily over one another, making graphite slippery.

The slippery property makes graphite perfect for lubricating machinery. The layers in pencil “lead” rub off onto paper when you write, leaving a dark mark.

Despite being made of carbon like diamond, graphite is soft and gray instead of hard and clear. The different arrangement of carbon atoms creates completely different properties.