Primitive helium in diamonds. 
Thirteen diamond stones from various unspecified mines in South Africa were analyzed for the isotopic ratio of helium-3 to helium-4.  Values of the ratio ranged from less than 10(-7) to (3.2 +/- 0.25) x 10(-4).  The latter value is higher than the primordial helium-3/helium-4 ratio in meteorites and close to the ratio for solar-type helium.  Such extremely high values may represent primitive helium that evolved very little (that is, showed very little increase in radiogenic helium-4) since the formation of the earth.