ИСТИНА

Kimberlite pipes essentially differ on a grade and morphology of diamond crystals. These parameters are controlled by two main factors: conditions of kimberlite formation in mantle and thermodynamics of kimberlite during its passage through the earth crust. Based on the trend in ilmenite composition, we arrived at the conclusion that the crystallization of the kimberlite groundmass in poor diamonds bearing pipes had been proceeding slower and at lower temperatures than in the rich pipes. These factors could bring about dissolving of small diamond crystals and destruction of defective crystals. The differences in kimberlite melt evolution resulted in differences of diamond grades of kimberlite pipes. This should be taken into account when exploring and prospecting for diamonds. Although the conditions for diamond formation may be favorable on the early stage, the dissolving of diamond crystals may happen afterward.