According to empirical evidence from evolutionists, geologists, etc., diamonds were formed about 1–3 billion years ago, which is earlier than any known record of even the Earth’s first land plants let alone coal. Coal, known as a fossil fuel, is formed from the long dead remains of vegetation, animals, and basically any organic material. The formation of coal takes millions of years and can be traced back to 300 to 400 million years ago, but certainly not a billion years (or more). So how are diamonds supposed to have formed from coal that didn’t even exist? They didn’t.
Natural diamonds require very high temperatures (ranging from 900 to 1300 Celsius) and pressures that exists only at depths of 87 to 120 miles (140 to 190 kilometers) in the Earth’s mantle to form. Unlike other gems which are formed by a combination of elements, diamonds are made up of one single element- Carbon (a diamond complex is an allotrope of carbon). Carbon-containing minerals present in the Earth at those depths crystallize to form diamonds because of the immense pressure together with the heat from molten magma, among other factors.
The diamond crystals are then transported to the surface during deep-source volcanic eruptions. When the magma cools, it forms igneous rocks known as kimberlites (named after the diamond-bearing region of Kimberly, South Africa where these rocks were first identified) and lamproites, used as an indicator that diamonds may be found in that area. The Kimberlites form narrow pipe shaped fissures which are also referred to as diamond pipes. The most prominent kimberlites are located in South Africa and Central Africa which roughly contributes for 49% of the natural diamonds mined in the World (think “blood diamonds”).
Conclusion: diamonds from carbon, not coal.
[Reposted (with editing) from Misconception Junction]