How do the structures and properties of diamond and graphite differ even though both are made of carbon?

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A rough, translucent yellow crystal of elemental sulfur displayed against a solid black background. — crystal A crystal form of elemental sulfur. Sulfur has an atomic weight of about 32.06 atomic mass units (amu), which means that its molar mass is 32.06 grams.

Diamond and graphite are allotropes of carbon, meaning they are different crystalline forms of the same element. Their distinct properties arise from how their atoms are arranged.1

Diamond

Diamond features an infinite three-dimensional tetrahedral network where each carbon atom is covalently bonded to four others. This rigid, compact structure requires the rupture of many strong bonds to break, resulting in extreme hardness, high thermal stability, and insulating properties.1

Graphite

Graphite consists of parallel sheets of carbon atoms arranged in fused hexagonal rings, known as graphene. While bonds within these layers are strong, the layers are held together by weak van der Waals forces. This structure allows the layers to slide over one another, explaining graphite's softness and lubricity. Additionally, the arrangement facilitates electrical conductivity and allows other molecules to penetrate between the layers.1

At room temperature and atmospheric pressure, graphite is more stable than diamond, though the conversion of diamond to graphite is extremely slow.1