“Diamonds are formed from compressed coal”

It's a widely held belief that diamonds are simply lumps of coal that have undergone intense pressure, a notion perhaps reinforced by popular culture, like fictional characters compressing coal into sparkling gems. This misconception likely stems from the fact that both diamonds and coal are primarily composed of carbon, and both form underground under specific geological conditions. The idea of transforming a common, dark material into something rare and brilliant is certainly appealing and makes for a compelling story.

However, the scientific reality of diamond formation tells a much older and more profound tale. Most natural diamonds are formed from pure carbon deep within the Earth's mantle, typically 90 to 150 miles below the surface. Here, temperatures soar above 2,000 degrees Fahrenheit, and the pressure is immense—approximately 50,000 times that of the atmosphere at sea level. These extreme conditions, sustained over billions of years, cause carbon atoms to crystallize into the incredibly strong, tetrahedral structure of a diamond. These ancient gems are then brought closer to the surface through rare, violent volcanic eruptions, where they are found embedded in unique igneous rock formations called kimberlite pipes.

The crucial evidence debunking the coal-to-diamond myth lies in their respective origins and ages. Coal is formed from decayed plant matter buried in sedimentary layers relatively close to the Earth's surface, typically no more than a few miles deep. The earliest land plants, which are the source material for coal, appeared about 450 million years ago. In stark contrast, the vast majority of natural diamonds are much older, with many dating back 1 to 3.5 billion years—long before any land plants existed on Earth. This significant age difference, combined with the vastly different depths and geological processes involved, clearly illustrates that diamonds do not originate from coal. While both are carbon, their journeys beneath the Earth's surface are worlds apart.