Mineralogy and Gemmology

Evaluation of diamond potential of the prospecting regions based on the study of morphology and chemical composition of accompanying minerals

Method was created at the Diamond Deposits Laboratory of the Lomonosov Moscow State University. The new technique of evaluation of diamond potential of the prospecting regions is based on study of morphology and chemical composition of garnets, ilmenite, chromites and other minerals accompanying diamonds in kimberlitic groundmass.

Division of indicator minerals into morphogenetic groups
and the prospecting works

The method includes sampling and selection of mono-mineral fractions of garnets, chromites and ilmenite and analysis of their morphological characters and chemical composition.

The method employs the use of several computer programs: programs for quantitative analysis of optical and SEM images and programs for the statistical analysis of electron microprobe data. Comprehensive studies of KIM are conducted in several stages:

1       identification and description of the different morphological types of KIM on the basis of optical and electron microscopy;

2       separation of genetic groups of garnets, ilmenite and chromites on the basis of the features of their composition and physical properties;

3       statistical analysis of materials, typification and localization of diamond-bearing rocks;

4       evaluation of primary sources of diamonds.

Division of indicator minerals into morphogenetic groups and economical estimation of diamond deposits

The method takes into account the conditions of preservation of diamonds and associated minerals during transporting from the mantle source to the surface in the kimberlitic magma. Changes in mineral surface characteristics (corrosive relief) and peculiarities of the internal structure of the grains indicate unfavorable conditions of preservation of diamonds in kimberlites and hence low diamond grades.

Another new technique of evaluation of diamond potential of kimberlites, based on study of chemical composition of microphenocryst (less than 100 micron) oxides from kimberlite groundmass.

Duration ? 1 month.

Authors: Prof. V.K.Garanin, Associate Prof. T.V.Posukhova,

Chair of Mineralogy, Faculty of Geology of Moscow State University