How do volcanoes make diamonds?

Before you say yes to that proposal, where DID your diamond come from?

Diamonds are hot stuff – they have been an important status symbol for hundreds of years, and form under extremes of heat and pressure, here’s how:

Diamonds are often found in Kimberlite or Lamproite pipes, these are sub-vertical rocks that formed when magma from deep within the Earth forced its way into shallower levels of the Earth and solidified. This magma (molten rock) may have originated from >100 miles (>160 km) deep, within the mantle. At this depth the rocks can experience very high pressures and temperatures that allow carbon to crystallise as diamonds as the magma rises towards the surface and cools.

If these deep magmas squeezed their way up to the surface of the Earth and erupted then diamonds may have been incorporated into volcanoes. However, our diamonds generally formed 1 – 3 billion years ago, so any evidence of volcanoes has long gone. We now collect all of our diamonds from Kimberlite and Lamporite pipes – areas where the solidified diamond-bearing magma is now exposed.

Fun fact:

  • The worlds oldest diamond is 4.3 billion years old, the width of a couple of human hairs (70 micrometers),  and was found in the Jack Hills of Australia in 2007