Where do largest diamonds on Earth come from?

Vast majority of diamonds are small in size but from time to time people also discover really large diamonds. The largest diamonds are usually the oldest diamonds because these diamonds had the most time to develop their size, and they most often come from cratons, the parts of the continental interior which contains the oldest rocks on planet. This is really no surprise since the oldest diamonds on our planet are almost as old as our planet is.

Most of the large diamonds that have been found so far arrived at the surface accidentally as byproducts of volcanic eruptions of deep magma that solidified into rocks called kimberlites. According to the scientists the inclusions of diamonds into these rocks come in two major varieties: peridotitic and eclogitic.

Peridotite is the most abundant rock type in the upper mantle, while eclogite is the remnant of oceanic crust recycled into the mantle by the sinking of tectonic plates.

The latest discovery by the scientists from South Africa showed that before 3.2 billion years ago, only diamonds with peridotitic compositions formed – while at the period around 3 billion years ago was dominated by eclogitic diamonds.