Abstract :
In studying the physical and geochemical properties of diamond, data on both elemental composition and defect structures is required. While instrumental neutron activation analysis is an essential component of this formidable analytical task, it is incapable of providing essential data on the lightest elements. This is accessible quantitatively by the use of accelerator-produced beams of protons, helium-3, helium-4 and fluorine-19 (or nitrogen-15). The picture that emerges is that all pure diamond is in elemental terms - characterized by no fewer than 58 impurities, of which 53 of these elements have been determined by nuclear methods, and 34 of them have been determined only by nuclear methods. If quantitative analytical data is obtained, as it should be, then a number of deductions can be made about the chemistry of the elemental impurities - such a trace element chemistry (at the ppb to ppm level!) is found to exist, which brings into focus the question of the mode of physical occurrence of these characteristic chemical impurities. Since they are not visible and appear to be fairly homogeneously distributed, a reasonable picture is to describe all diamonds (even those of the purest gemquality) as containing sub-microscopic inclusions of the parental magma in and from which the diamond crystallized. This brings with it a fresh challenge: can this type of "magma droplet" inclusion be identified physically and, indeed, what can be deduced about the sub-microscopic defect structures in diamond.
