SIMPLE IDENTIFICATION AND QUANTIFICATION OF MICRODIAMONDS IN ROCK THIN-SECTIONS

Abstract

Using a method of preparing polished thin-sections described in this paper, we are able to detect microdiamonds in high-pressure metamorphic rocks quickly and quantitatively by a distinctive striation pattern on the polished surface of the thin-section. We present results on samples from diamondiferous gneiss and marble of the Lake Kumdyd-Kol region of the Kokchetav Massif, Northern Kazakhstan. OUr method clearly reveals microdiamonds as small as 1 μm by a striation pattern as soon as they emerge on the surface during the polishing procedure. the striation pattern on the polished surface disappears almost immediately after extraction of the microdiamond that caused it. More than six hundred polished thin-sections of various kinds of igneous and metamorphic rocks mostly without a high=ressure origin were examined, but this type of striation pattern was found in less than 1% of these. In such examples the striations could also be due to the contamination of diamond from external sources.