Superdeep diamonds from the Juina area, Mato Grosso State, Brazil

Characteristics of Nitrogen and Other Impurities in Diamond, as Revealed by Infrared Absorption Data

“…For the purposes of this investigation, we have analyzed IR spectra of several thousand diamond crystals, compiled and interpreted during the course of our studies of the Siberian (Yakutian), Arkhangelsk, Uralian, South African, Canadian, Venezuelan and Brazilian diamond fields during the period 1980s -1990s. This study complements our previously published preliminary results on diamond crystals from these deposits (e.g., Blinova 1987, Blinova et al 1985, 1991, Smirnov et al 1986, Kaminsky et al 2000, 2001.…”

“…A peculiar feature of diamond crystals from the Newlands and Jagersfontein kimberlites in South Africa is an above-average proportion of type-IIa diamond crystals (up to 60% in the Jagersfontein pipe), and the predominance of pure type-IaA diamond crystals and crystals with a low degree of nitrogen aggregation among nitrogen-rich diamond crystals (Menzies et al 1998, Chinn et al 1998. Examination of optically active defects in diamond crystals of the newly discovered super-deep paragenesis (with ferroan periclase + magnesium-substituted perovskite and other specific inclusions) reveals that the diamond is predominantly of type IIa , Harte et al 1999, Davies et al 1999, Kaminsky et al 2001.…”

Manganilmenite in the Magnetite Ore Body from Pokphur Area of Nagaland, North East India and the Possibility of Microdiamonds in the Ophiolites of Indo-Myanmar Ranges

“…McCallum 23 noted relative abundance of Mn-ilmenite at several widely separated and mostly diamondiferous kimberlite localities, which supports its value in exploration. Kaminsky et al 15 too found a series of low-Mg manganoan ilmenite inclusions in Juina placer diamonds in which the MnO content varies from 0.42 to 2.12 wt%; in two grains MnO reaches 6.01 and even 11.46 wt%. MgO content in all these grains is very low (<0.81 wt%).…”

“…Most of the literature deals with its origin and summarily manganilmenite formed at the latest magmatic or postmagmatic, metasomatic stages and manganilmenite inclusions in diamonds are primarymagmatic. The importance of manganilmenite has been increasing in exploration as a diamond indicator mineral since Tompkins and Haggerty 14 , and Kaminsky et al 15 recommended that it be included in the list of diamond indicator minerals. To our knowledge, manganilmenite has not been reported from the Indian sub-continent until the present authors indicated its presence in the recent past 16 .…”

“…However, Tompkins and Haggerty 14 , and Kaminsky et al 15 recommended that it be included in the list of diamond indicator minerals. This is because lowmagnesian ilmenite (with only 0.11-0.14 wt% MgO) was first reported as an inclusion in three 'Brazilian' diamonds by Meyer and Svisero 22 , who noted that it has a stoichiometric composition with major impurity of manganese (MnO: 0.64-0.75 wt%).…”