Diamonds were most commonly formed around 100 miles below the surface of the Earth some 3 billion years ago. But diamonds can also be formed from asteroids impacting with the Earth’s surface. Such collisions from large asteroids, travelling at speeds of 9 – 12 miles per second, would include enormous pressure and intense heat (as hot as the surface of the sun). These are adequate conditions for diamond formation.
In some cases diamonds formed in outer space can find their way to Earth via meteorites.
Synthetic diamond production has produced diamonds that are not suitable for jewelry. But their composition remains ideal for the kind of abrasion that can be used in drilling and fine cutting equipment.
So, all the precious diamonds available to miners and jewellers appear to already exist, save for a rogue asteroid collision. They just need to be found.
How are diamonds actually formed?
As previously stated the conditions under which diamonds are formed include intense heat and pressure. Under such conditions carbon atoms crystallise and it is this crystallisation that forms the diamonds.
Are diamonds mined at depths of 100 miles below the surface of the Earth?
No. Volcanic eruptions known as Kimberlite eruptions force the diamond-containing rocks upward to be mined at more reasonable depths of around 1000 metres. Diamond mining is not without its risks. Mining anything at a 1000 metre depth obviously presents its own challenges. Especially when you consider that the purpose of the endeavour is to break down the rock that holds the mines in place. Precision and effective mapping are key features in diamond mining whose tunnels run like a labyrinthine network.
Kimberlite eruptions are rare. The last known eruption was around 25 million years ago with most happening during the Cretaceous period 146 to 65.5 million years ago.
Are diamonds formed from coal?
No. There is no evidence to suggest that diamonds are formed from coal. Coal is formed from a process involving organic material that falls into water, ideally swamp, which preserves it from decay since swamp waters are usually deficient in oxygen. Oxygen accelerates decay.
Furthermore, insects and creatures that may feed on the plant life above water would not survive well beneath the surface of swamp water in an oxygen deficient environment.
To form the thick layer of plant debris required to produce a coal seam, the rate of plant debris accumulation must be greater than the rate of decay. Once a thick layer of plant debris is formed, it must be buried by sediments such as mud or sand. These are typically washed into the swamp by a flooding river. The weight of these materials compacts the plant debris and aids in its transformation into coal. About ten feet of plant debris will compact into just one foot of coal.https://geology.com/rocks/coal.shtml
Why is a swamp biome the perfect environment for mining diamonds in Minecraft?
Well, maybe this was once true and probably as much to do with the myth that diamonds are formed from coal as anything else. But in reality you will find diamonds in any biome with perhaps a higher probability of finding them in swamp, desert, mesa and savanna biomes. You’re much less likely to find anything like diamonds beneath the sea floor.
Ravines are a great source of diamonds and rare minerals since they expose to depths of 12Y and a simple staircase or ladder route down will enable you to find them with ease. Or, if you’re a daredevil, just jump straight into a puddle of water and worry about getting back up at a later date!
Where can I find more on the production and mining of diamonds?
Geology.com has some fantastic resources that detail the environment and conditions suited to diamond production.
Some additional resources
For a slightly more geo-political account of diamond mining in Africa, the book Stones of Contention: A History of Africa’s Diamonds (Africa in World History) is highly recommended.