1. Diamond, a particular form, or allotrope, of carbon, is the hardest material we know of. It’s more than twice as hard as the closest competition, silicon nitride and cubic boron nitride.
2. That extraordinary hardness arises from a strong and inflexible structure: Five atoms form a tetrahedron and share electron pairs with each other.
3. In nature, diamond is typically created under extremes of pressure and temperature, deep in Earth’s mantle — about 90 miles or more beneath our planet’s surface.
4. Except for space diamonds, of course. In 2017, researchers re-created, for the first time, the conditions under which they believe diamond rain forms in Uranus and Neptune.
5. These planets have internal temperatures just right for diamond formation. As hydrocarbon gases sink toward their cores, increasing pressure squeezes out the hydrogen atoms and presses the remaining carbon into diamond, which travels through the planet’s heart as very ...
