What is The Age of Diamond ?
Diamond grew in its host rock, kimberlite. Most, if not all, gem-quality diamonds have an origin deep in the Earth’s crust or mantle and have been transported to the surface as crystals or rock fragments by fluid, volcanic kimberlites. Therefore diamonds are older that their host kimberlites and dating them has to rely on microanalysis of their inclusions.
Such work indicates that the oldest diamonds found so far are about 3300 Ma old, and stones of this age occur in the Kimberley and Finsch kimberlite pipes in South Africa. Slightly younger diamonds, 2900 Ma old, occur in the Orapa kimberlite in Botswana, accompanied by even younger stones ‘only’ 990 Ma old. The age of the kimberlite host rock at Orapa has also been determined and is significantly younger than its diamonds at 93 Ma. So in many kimberlites, minerals and rocks of vastly different ages may exist side by side.
The very old ages for diamonds obtained from isotope analyses are given some support by stratigraphic evidence for diamonds at least 2500 Ma old in South Africa. The Witwatersrand quartzites and conglomerates
are ancient sediments which contain alluvial diamonds. The sediments were folded and metamorphosed 2500 Ma ago, so the diamonds must have come from an even older source.