“Diamonds are formed from compressed coal”

It's a widely held belief that diamonds are formed from highly compressed coal, but this common notion doesn't quite align with geological reality. In truth, the vast majority of natural diamonds are far older than the first land plants that eventually formed coal, predating them by billions of years. This fundamental difference in age and origin is key to understanding why the idea of coal transforming into diamonds is a myth.

Natural diamonds actually crystallize from pure carbon under immense heat and pressure, deep within the Earth's mantle, typically at depths of 90 to 120 miles. These extreme conditions, involving temperatures over 2,000 degrees Fahrenheit and pressures over 725,000 pounds per square inch, existed between one and three billion years ago. Coal, on the other hand, forms much closer to the Earth's surface, from the buried remains of ancient land plants that lived only a few hundred million years ago. The conditions for coal formation are nowhere near intense enough to create diamonds.

The misconception likely stems from a simplified understanding of both materials. Both coal and diamonds are primarily composed of carbon, and both are associated with formation under pressure. Since coal is a familiar carbon-rich material found underground, it's an understandable, though incorrect, leap in logic to assume that with enough time and pressure, it could become a diamond. However, the specific geological environments and timescales required for each are vastly different, making the "coal to diamond" story a compelling but ultimately inaccurate tale.