The First Results of a Study of Large Diamonds from Industrial Deposits of Yakutia

A representative amount of diamonds larger than 10.8 carats extracted from deposits of Yakutia during separate ore processing of each kimberlite pipe has been studied for the first time. It is shown that, according to the diamond typomorphic characteristics of habit, nitrogen content, and aggregation, as well as hydrogen concentration in diamond, it is possible to carry out a preliminary evaluation of the deposit to predict the presence of large and giant diamonds. It has been established that large diamonds from the deposits of the Daldyn-Alakitsky area have wide variations of nitrogen impurity and its aggregations in comparison with diamonds from the Malobotuobinsky and Srednemarkhinsky areas. It is determined that the content of large diamonds in the pipes of Yakutia is inversely proportional to the number of rounded dodecahedroids. The most promising deposits for finding large diamonds are those in which the majority of diamonds belong to one population—average nitrogen low-aggregated diamonds that were formed at a temperature of ~1100°C. According to the study of geological collections of diamonds, it is shown that, in kimberlite pipes with an increased nitrogen content in diamonds, an increase in the proportion of large diamonds in the deposit is noted. On the contrary, according to the aggregation of nitrogen in diamonds, as a parameter of postgrowth history, there is a negative correlation with the content of large diamonds. An increased value of the concentrations of hydrogen in diamonds not only negatively affect the total diamond content of the deposit, but also generally control the decrease in the content of large diamonds.