ИСТИНА

The peculiarities of microcrystalline oxides from groundmass in 10 pipes of Arkhangel kimberlite province were investigated by optic and microprobe methods. The results of our investigation show, that the connection between chemical composition of the microcristalline oxides from kimberlite groundmass and quantity and quality of diamond crystals exists. The conditions of high contents of diamond are following: - the presence of high-Cr-picrocromites of the first cluster group with >53.0 wt.% Cr2O3,< 3.5 wt.% TiO2 and 9.0-14.0 wt.% MgO, - absence and low content ( < 25% in accidental statistical reliable grains selection) of the titanomagnetites and other Ti-mineral-phases (ilmenites, rutiles, perovskite, sphen). The conditions of low contents of diamond are following: - the prevalence of Mg-Cr-Al-titanomagnetites and magnetites of the eight and ten cluster group and Mg-Cr-ulvospinels of sixth and seventh cluster groups with <35.5 wt.% Cr2O3, 3.5-17.0 wt.% TiO2 and 19.5-54.0 wt.% Fe2O3, - at the case, when the content of the titanomagnetites and other Ti-mineral-phases ( ilmenites, rutiles, perovkite, sphen) in accidental statistical reliable grains selection is more than 75%