Carbon isotopic variation in spectral type II diamonds

The carbon isotope composition of most diamonds measured so far1 falls within a fairly restricted range from −5 to −9‰. On the other hand, the type II diamonds studied here show δ13C values (−0.5 to −31.9‰) extending over almost the entire range of carbon isotope values previously quoted for diamonds. We suggest here that these data are related to variations in the nature of the carbon reservoir source and associated inclusion suites.