“Diamonds are formed from compressed coal”

The idea that diamonds are simply compressed coal is a widespread and enduring misconception, likely stemming from a few understandable points of confusion. Both substances are carbon-based and are found underground, formed under pressure, making a superficial connection seem plausible. Popular culture, notably through depictions like Superman squeezing coal into diamonds, has also cemented this image in the public consciousness, suggesting a direct, transformative link.

However, the scientific reality of diamond formation tells a different, far more ancient story. Most natural diamonds formed between one and three and a half billion years ago, deep within the Earth's mantle, at depths of 90 to 120 miles. These extreme conditions, with temperatures soaring above 2,000°F and immense pressure, cause carbon atoms to crystallize into the incredibly strong diamond structure. Crucially, this timeframe for diamond creation predates the existence of land plants, which are the fundamental source material for coal, by hundreds of millions of years. Coal, in contrast, forms from decayed plant matter in much shallower geological settings, typically within a few miles of the Earth's surface.

While both coal and diamonds are made of carbon, their origins are geographically and chronologically distinct. Diamonds are primarily formed from carbon-rich fluids or primordial carbon present in the mantle, brought to the surface through rare volcanic eruptions in kimberlite and lamproite pipes. The occasional, rare diamond found in subduction zones might involve organic carbon, but this is not the typical or primary formation pathway. Therefore, despite the popular myth, the vast majority of natural diamonds have no connection to coal.