Which combination of factors leads to diamond formation?

• A. Carbon, high temperature, and high pressure
• B. Silicate minerals, low temperature
• C. Water-rich fluids at low pressure
• D. Organic matter at surface

Answer: (A)

Diamond forms when carbon is subjected to the extreme pressures and temperatures found deep in the Earth's mantle. The carbon source is essential, and under these intense conditions the atoms rearrange into the very strong, three-dimensional lattice of diamond. At high pressure, the diamond structure becomes more stable than other forms of carbon, and high temperature helps atoms move into the orderly arrangement. The other scenarios don’t provide both the necessary pressure and temperature: silicate minerals at low temperature lack the environment needed to drive the carbon into the diamond lattice; water-rich fluids at low pressure cannot push carbon into the dense crystal form; organic matter at the surface experiences low pressure and typically ends up as graphite or is altered by weathering rather than forming diamonds. So the key combination is carbon plus very high pressure and high temperature, originating deep in the mantle and brought close to the surface by deep-origin magmas.