The formation of diamonds begins as the bare element of carbon deposited beneath the surface of the Earth. Since it is contained in most minerals, they continue to grow for around 1 to 3 billion years. This carbon mineral undergoes the most extreme conditions of temperature and pressure at depths of about 120 miles from the mantle of the Earth.
The carbon piece then travels upward through volcanic eruptions and magma flows. These particles then cool into the igneous rocks where they are mined out and converted into costume diamond rings and other jewelry.
The phenomenon of the magma flow is quite rare, and when it occurs, we get to see solidified lava forms s known as Kimberlite. This is left beneath the Earth’s crust and they usually contain diamond deposits, which are then mined to trade. These may not have diamond crystal deposits sometimes though, such as in the ones found in unlikely places like glacial movement sites.