SIMPLE IDENTIFICATION AND QUANTIFICATION OF MICRODIAMONDS IN ROCK THIN-SECTIONS

Using a method of preparing polished thin-sections described in this p aper, we are able to detect microdiamonds in high-pressure metamorphic rocks quickly and quantitatively by a distinctive striation pattern o n the polished surface of the thin-section. We present results on samp les from diamondiferous gneiss and marble of the Lake Kumdy-Kol region of the Kokchetav Massif, Northern Kazakhstan. Our method clearly reve als microdiamonds as small as 1 mu m by a striation pattern as soon as they emerge on the surface during the polishing procedure. The striat ion pattern on the polished surface disappears almost immediately afte r extraction of the microdiamond that caused it. More than six hundred polished thin-sections of various kinds of igneous and metamorphic ro cks mostly without a high-pressure origin were examined, but this type of striation pattern was found in less than 1 % of these. In such exa mples the striations could also be due to the contamination of diamond from external sources.