Deciphering diamonds' origins

Scientists in Australia have developed a method for determining very low concentrations of elements in diamonds.   

The method, which uses a technique called laser ablation microprobe inductively-coupled plasma mass spectrometry (LAM-ICP MS), could help explain how natural diamonds are formed. 

Diamonds are known to originate deep within the Earth’s mantle, but the exact processes involved are still poorly understood. During formation, however, fluids can become trapped in the diamond, leading to tiny amounts of solids being deposited inside the diamond as it grows. These solids contain minute quantities of elements other than the carbon the diamond is made of.   

Sonal Rege and colleagues at Macquarie University have used LAM-ICP MS to drill tiny holes in diamonds and analyse the concentrations of these trace elements inside them. The element patterns they get can give important clues to the processes happening at the high temperatures and pressures needed to form diamonds.   

Rege suggests information like this could help improve diamond exploration, and also raises the possibility of diamond ’fingerprinting’. This could be used to identify diamonds from different areas, providing better controls on illicit diamond trading and allowing stolen goods to be traced to their origin. 

The technique can now be applied to detailed studies of diamonds from different places, but future research will not be without challenges. ’Most gem-quality diamonds contain very low levels of all trace elements,’ said Rege, ’so continued improvement of instrumental sensitivity will be needed’. Rowena Milan