🔬 Science Facts #14: Diamonds Are Compressed Coal Under Extreme Pressure

🔬 Science Facts #14: Diamonds Are Compressed Coal Under Extreme Pressure. Diamonds and graphite — the material used in pencils — are both made entirely of carbon, but different atomic arrangements create materials with completely opposite properties.. Diamonds, the hardest gemstone on Earth and a symbol of luxury, and graphite, the material used in ordinary pencils to write on paper — both are made of the same chemical substance: pure carbon. The dramatic difference between them — diamonds being extremely hard, shiny, and transparent; graphite being soft, black, and dull — is solely due to how the same carbon atoms are arranged in different structures. In diamonds, each carbon atom is bonded to four other carbon atoms in a three-dimensional structure called a tetrahedral lattice. Each bond in this lattice is very strong, and it is the overall three-dimensional strength that makes diamonds the hardest naturally occurring material — according to the Mohs scale, diamonds have a perfect score of 10. In graphite, carbon atoms are arranged in flat layers called graphene. In each layer, each carbon atom is bonded to three other carbon atoms forming a very strong hexagonal pattern. However, the bonds between these layers are very weak, allowing the layers to easily slide over one another — this is why graphite feels smooth and is good as a lubricant, and why it leaves a mark on paper when pressed. Under extremely high temperature and pressure approximately 1,000 degrees Celsius and pressure of 45,000-60,000 atmospheres , graphite can be converted into diamonds in a process used industrially to produce synthetic diamonds. Natural diamonds form deep within the Earth, about 160 kilometers below the surface, under suitable temperature and pressure conditions.