How diamonds are formed

Diamonds originate from kimberlite rock, formed billions of years ago in the Earth's mantle under extreme heat and pressure. These crystals grow over time and occasionally move closer to the surface through volcanic eruptions, becoming trapped in kimberlite pipes. Today, diamonds are mined from these pipes, cut, and polished to enhance their brilliance, making them highly prized gems.

What happens to diamonds as magma cools and solidifies?

Why are diamonds highly prized according to the text?