The idea that coal transforms into diamonds under immense pressure is a widely held belief. However, this popular notion is a geological misconception. Scientific understanding reveals that coal does not naturally turn into diamonds.
The Formation of Natural Diamonds
Natural diamonds form deep within the Earth’s mantle. These gems typically crystallize at depths ranging from about 90 to 120 miles (145 to 190 kilometers) below the surface. The temperatures at these depths are incredibly high, averaging between 1,650 and 2,370 degrees Fahrenheit (900 to 1,300 degrees Celsius). This intense heat combines with immense pressure, estimated at 4.5 to 6 gigapascals, which is roughly 45,000 to 60,000 times the atmospheric pressure at Earth’s surface.
The carbon source for natural diamonds is typically not surface organic matter like coal. Instead, it originates from ancient carbon-bearing fluids or rocks deep within the mantle. After their formation, diamonds are brought closer to the Earth’s surface through rapid volcanic eruptions. These eruptions occur via kimberlite and lamproite pipes. Most natural diamonds are ancient, with ages commonly ranging from 1 to 3.5 billion years.
The Origins of Coal
Coal is a combustible sedimentary rock primarily composed of carbon, formed from ancient vegetation. Its formation begins in swampy environments where dead plant matter accumulates in waterlogged conditions, preventing decay. Over millions of years, these layers of organic material become buried under sediments, subjecting them to increasing heat and pressure in a process known as coalification. This transformation converts the plant remains into coal.
The conditions under which coal forms are significantly different from those required for diamond crystallization. Coal typically forms at much shallower depths, usually only a few miles or kilometers below the Earth’s surface. The temperatures and pressures involved in coal formation are considerably lower than the extreme conditions found in the mantle where diamonds originate. While coal is mostly carbon, it also contains varying amounts of other elements, including hydrogen, sulfur, oxygen, and nitrogen, as well as other impurities.
Why Coal Cannot Turn Into Diamonds
The fundamental reason coal cannot transform into diamonds lies in the vastly different geological conditions required for their formation. Coal forms at relatively shallow depths under moderate heat and pressure, conditions insufficient to rearrange its carbon atoms into the tightly bonded crystalline structure of a diamond. Diamonds, conversely, demand extreme temperatures and pressures found only deep within the Earth’s mantle.
Another significant distinction is the carbon source itself. The carbon that forms most natural diamonds is ancient, originating from deep within the Earth’s mantle and often predating the existence of widespread plant life that forms coal. Coal, on the other hand, is derived from decomposed organic plant matter, which contains numerous impurities such as hydrogen, oxygen, and sulfur. These impurities prevent the pure carbon crystallization necessary for diamond formation, as diamonds are composed of nearly pure carbon. Therefore, despite both being carbon-based, their distinct origins and the vastly different geological environments they require mean that coal does not naturally turn into diamonds.