C

These samples of graphite are displayed in the Smithsonian Museum of Natural History. Graphite is a form of carbon. The sample at left is about 12 cm across and is from Canada.

Carbon in the graphite form is made up of layers of carbon atoms which can be induced to move relative to each other. It is used as a dry lubricant. It is much softer than carbon in the diamond form, which is the hardest mineral. Graphite has a hardness of 1-2 compared to 10 for diamond.

This sample is graphite with calcite from Ticonderoga, New York. The sample is about 15 cm wide.