Like diamonds, graphite is made solely of carbon. At the molecular level, both minerals are made of a series of dual pyramids connected in a lattice structure resembling a honeycomb. Regardless, the two are unlikely to be mistaken for one another.
Graphite is soft enough to be used as pencil lead, while its deep grey color is dark enough to contrast strongly against writing paper. In its rough form, it usually manifests in flakes, and veins and large crystals in magma derived rock.
By contrast, diamonds are the hardest stones known to science. While diamonds are used for a number of industrial purposes, their most famous appearance is for fine jewelry. They are colorless in their purest state, though they exist in a variety of colors due to trace elements mixed in their crystals. The rough stone closely resembles an eight sided die, and form under specific conditions 90 miles below the earth’s crust.
The place where diamonds and graphite diverge is in the nature of their molecular shapes. Graphite’s atomic structure is that of two hexagonal pyramids joined at their widest parts, while diamonds are made of two triangular pyramids fastened together at their square bases. This small detail makes a world of difference in their hardness, appearance and uses.