The stones, which are over 4bn years old, were found inside rocks lodged in the sediments of a coastal ridge known as the Jack Hills. It is hoped that they will shed light on the earliest period of the Earth's history, the Hadean period (the period between the planet's initial formation and the formation of the first rocks.). The oldest of the diamonds is thought to be 4.25bn years old. This would suggest that the Earth had cooled enough to form a crust of solid rock by that time, earlier than originally thought.
This is definitely in the “fascinating stuff” category. Geology isn’t my area of expertise (try mammalian physiology and microbiology, although university is a long time ago now...)