Do Diamonds Really Come From Coal

No, diamonds do not actually come from coal. While it's a common misconception, the formation of diamonds and coal involves different processes and conditions. Here's a detailed breakdown of why it's not true:

Depth and Formation Environments

Coal: Coal is a sedimentary rock formed from the compressed remains of ancient plants buried near the Earth's surface. The pressure comes from the weight of layers of sediment stacked on top, not the kind of intense pressure needed for diamonds.

Diamonds: Diamonds, on the other hand, form deep within the Earth's mantle, around 150-200 kilometers (90-125 miles) below the surface. This immense depth creates the extreme pressure (about 50,000 times atmospheric pressure) required for diamond formation.

Time

Most diamonds are dated to be billions of years old, far predating the existence of land plants like trees, which are the primary source material for coal. Coal formation is a much more recent geological phenomenon.

Compositional Differences

Coal contains various impurities like hydrogen, oxygen, nitrogen, and sulfur, along with carbon. These impurities prevent the pure carbon crystal structure required for a diamond.

Diamonds, in contrast, are nearly pure carbon (around 99.95%) with a highly ordered atomic arrangement.

Where Do Diamonds Really Come From?

The most likely scenario for diamond formation involves carbon sources deep within the Earth's mantle:

Primordial Carbon Deposits: These carbon deposits could have been present since the formation of Earth itself.

Subducted Rocks: When oceanic plates (containing carbonate rocks like limestone and dolomite) sink beneath continental plates, the intense heat and pressure can break down these rocks, releasing carbon that contributes to diamond formation.

Asteroid Impacts: The immense heat and pressure from a massive asteroid hitting Earth could potentially create diamonds as well, although this is thought to be a less common occurrence.

The Journey to the Surface

Once formed deep within the mantle, diamonds need a way to travel the vast distance to the Earth's surface. This incredible journey is facilitated by:

Kimberlite Pipes

Kimberlite pipes are carrot-shaped geological formations that are the primary source of mined diamonds today. They are vertical tubes of igneous rock that breach the Earth's crust, originating from deep within the mantle. Kimberlite itself is a rare, ultramafic volcanic rock rich in magnesium and iron.

Violent volcanic eruptions called kimberlite eruptions can carry diamonds upwards in a fast, pressurized flow. Unfortunately, not all kimberlite pipes contain diamonds, and even those that do may have very few. The likelihood of finding diamonds depends on whether the kimberlite pipe actually sampled a diamond-bearing region of the mantle during its upwards journey.

Conclusion

In summary, diamonds and coal share the element of carbon, but they have distinct geological origins and form under completely different conditions. Diamonds come from the Earth's mantle through a process involving high pressure and high temperature, while coal forms from the compression of plant material in swampy environments.