NUCLEAR MICROSCOPY OF RUBIES - TRACE-ELEMENTS AND INCLUSIONS

The concentrations of trace elements (e.g. Ti, V, Cr, Fe and Cu) in or namental rubies have been linked to the country of origin for natural stones [1, 2]. These broad-beam PIXE results show relatively large var iations between stones from one country, which might indicate that the y stem from different geological environments in a country, or that th ere are inclusions or surface contaminations present in individual sto nes. PIXE elemental maps were used to find contamination and inclusion free regions on rubies from Mong Hsu, Burma, and from Thailand. Trace element concentrations were determined in these surface areas. The re sults indicate that the Fe-concentrations in Mong Hsu rubies have prev iously been overestimated due to the presence of surface contamination s. Cu is consistently present at a few hundred ppm level in these ston es and not observed in any of the four Thai rubies, while it was obser ved sporadically in broad-beam measurements. The depth profiling capab ilities of the proton microprobe were employed for the analysis of liq uid and mineral inclusions in rubies, and some preliminary results are reported.