The team first cut 24 diamonds into slices and looked at their growth structures under an electron microscope. Then they analysed what minerals, trace elements and isotopes had become trapped inside the diamonds as they formed. It's the first time such an analysis has been carried out. They discovered the diamonds had high helium 3 to helium 4 ratios, confirming the primordial reservoir exists either at the depth at which the diamonds were formed or below them in the lower mantle. Professor Foley said the study clears up an age-old controversy, and shows how crucial diamonds are as the only samples we have to give us ... (full story)