Peculiarities of Diamonds in Eclogitic Xenoliths from the Komsomolskaya Kimberlite Pipe,Yakutia

The first studies of diamonds in eclogitic xenoliths from the Komsomolskaya kimberlite pipe are described. Among round and oval-shaped xenoliths with diamond ingrowths, samples with a garnet content of 40–90% of the xenolith volume dominate. Two eclogite samples contain grains of accessory rutile; a kyanite sample is also revealed. Certain samples contain two or more crystals of diamonds. Diamonds with an octahedral habit and crystals with transitional habits, which belong to an octahedral-rhombic dodecahedral row, dominate in eclogites; there are many variety VIII aggregates. A high concentration of structural nitrogen, commonly in the A form, was registered in most of the crystals. Diamonds with a small content of nitrogen impurities, 40–67% in the B1 form, are present in a number of xenoliths. The calculated temperatures of the formation of eclogitic xenoliths is 1100–1300°C. Diversity in the impurity compositions of diamonds in the same xenolith shows that these diamonds were formed at various times and in different settings. The diamond position in xenoliths, the various level of nitrogen aggregation in the diamonds, and a number of other factors point to the later formation of the diamonds, as compared to minerals of eclogites, from fluid or fluid-melts in the process of metasomatosis.

     

Carbon isotopic composition of diamonds in Ukraine and their probable polygenetic nature

The paper presents newly obtained data on the mineralogical and geochemical characteristics of Ukrainian endogenic and supergenic diamonds, including pioneering data on the carbon isotopic composition of individual diamond crystals. The endogenic diamonds occur as euhedral microcrystals (their morphology varies from octahedral to rhombododecahedral and cubic) with broadly varying concentrations of the structural nitrogen admixture and with mostly low aggregation of nitrogen centers. According to their carbon isotopic composition, Ukrainian diamonds range from kimberlitic–lamproitic to metamorphic and even carbonado-like, i.e., are polygenetic. Our data confirm the earlier conclusion that the supergenic diamonds are of impact genesis.     

Formation of mosaic diamonds from the Zarnitsa kimberlite

Mosaic diamonds from the Zarnitsa kimberlite (Daldyn field, Yakutian diamondiferous province) are morphologicaly and structurally similar to dark gray mosaic diamonds of varieties V and VII found frequently in placers of the northeastern Siberian craton. However, although being similar in microstructure, the two groups of diamonds differ in formation mechanism: splitting of crystals in the case of placer diamonds (V and VII) and growth by geometric selection in the Zarnitsa kimberlite diamonds. Selective growth on originally polycrystalline substrates in the latter has produced radial micro structures with grains coarsening rimward from distinctly polycrystalline cores. Besides the formation mechanisms, diamonds of the two groups differ in origin of mineral inclusions, distribution of defects and nitrogen impurity, and carbon isotope composition. Unlike the placer diamonds of varieties V and VII, the analyzed crystals from the Zarnitsa kimberlite enclose peridotitic minerals (olivines and subcalcic Cr-bearing pyropes) and have total nitrogen contents common to natural kimberlitic diamonds (0 to 1761 ppm) and typical mantle carbon isotope compositions (-1.9 to -6.2%c 5¹³C; -4.2%c on average). The distribution of defect centers in the Zarnitsa diamond samples fits the annealing model implying that nitrogen aggregation decreases from core to rim.     

Petrology and geochemistry of a diamondiferous lherzolite from the Premier diamond mine, South Africa

This paper reports on the petrology and geochemistry of a diamondiferous peridotite xenolith from the Premier diamond mine in South Africa.

The xenolith is altered with pervasive serpentinisation of olivine and orthopyroxene. Garnets are in an advanced state of kelyphitisation but partly fresh. Electron microprobe analyses of the garnets are consistent with a lherzolitic paragenesis (8.5 wt.% Cr₂O₃ and 6.6 wt.% CaO). The garnets show limited variation in trace element composition, with generally low concentrations of most trace elements, e.g. Y (<11 ppm), Zr (<18 ppm) and Sr (<0.5 ppm). Garnet rare earth element concentrations, when normalised against the C1 chondrite of McDonough and Sun (Chem. Geol. 120 (1995) 223), are characterised by a rare earth element pattern similar to garnet from fertile lherzolite.

All diamonds recovered are colourless. Most crystals are sharp-edged octahedra, some with minor development of the dodecahedral form. A number of crystals are twinned octahedral macles, while aggregates of two or more octahedra are also common. Mineral inclusions are rare. Where present they are predominantly small black rosettes believed to consist of sulfide. In one instance a polymineralic (presumably lherzolitic) assemblage of reddish garnet, green clinopyroxene and a colourless mineral is recognised.

Infrared analysis of the xenolith diamonds show nitrogen contents generally lower than 500 ppm and variable nitrogen aggregation state, from 20% to 80% of the ‘B’ form. When plotted on a nitrogen aggregation diagram a well defined trend of increasing nitrogen aggregation state with increasing nitrogen content is observed. Carbon isotopic compositions range from −3.6 ‰ to −1.3 ‰. These are broadly correlated with diamond nitrogen content as determined by infrared spectroscopy, with the most negative C-isotopic compositions correlating with the lowest nitrogen contents.

Xenolith mantle equilibration temperatures, calculated from nitrogen aggregation systematics as well as the Ni in garnet thermometer are on the order of 1100 to 1200 °C.

It is concluded that the xenolith is a fertile lherzolite, and that the lherzolitic character may have resulted from the total metasomatic overprinting of pre-existing harzburgite. Metasomatism occurred prior to, or accompanied, diamond growth.     

Aspects of diamond mineralisation and distribution at the Helam Mine, South Africa

The diamonds from the Swartruggens dyke swarm are mainly tetrahexahedra, with subsidiary octahedral and cuboid crystals. They are predominantly colourless, with subordinate yellows, browns, and greens. The existence of discrete cores and oscillatory growth structures within the diamonds, together with the recognition of harzburgite, lherzolite, at least two eclogitic and a websteritic diamond paragenesis, variable nitrogen contents, and both Type IaAB and Type Ib–IaA diamonds provides evidence for episodic diamond growth in at least six different environments. The predominance of plastic deformation in the diamonds, the state of nitrogen aggregation, and the suite of inclusion minerals recovered are all consistent with a xenocrystic origin for the diamonds, with the Type Ib–IaA diamonds being much younger than the rest. Mantle storage at a time-averaged temperature of ±1100 °C is inferred for the Type IaAB diamonds. The distribution of mantle xenocrysts of garnet and chromite within the high-grade Main kimberlite dyke compared to the low-grade Changehouse kimberlite dyke strongly suggests that the difference in diamond content is due to an increased eclogitic component of diamonds in the Main kimberlite dyke.     

Spectroscopic constraints on growth of Siberian mixed-habit diamonds

Notable within-crystal variability of mineralogical and geochemical properties of single natural diamonds are commonly attributed to changing chemistry of parental fluids, sources of carbon and redox conditions of diamond precipitation. A distinct type of compositional heterogeneity (mixed-habit structure) is well-known to occur in diamonds as well as in many other minerals due to purely “structural” reasons that are unequal crystal chemistry of crystallographically different faces and selective absorption and fractionation of impurities between adjacent growth pyramids. Based on the combined cathodoluminescence, Fourier-transformed infrared spectroscopy and photoluminescence spectroscopy, study of nine diamond crystals with different growth histories and external morphology, but all showing mixed-habit patterns at different growth stages, we show that mixed-diamonds may grow in closed system conditions or with a slowly decreasing growth rate from a media with a much lower impurity content than previously thought. Intracrystal nitrogen distribution seems to be a function of growth rate even in the cases of unusual impurity partitioning between growth sectors. Generally poor with IR-active hydrogen at moderate nitrogen aggregation parameters, studied diamonds likely resemble the low hydrogen content from the growth medium that, for cubic diamonds, was typically suggested hydrogen-rich and a crucial factor for growth of cubic and mixed-habit diamonds. We also show that mixed-habit diamond growth may occur not only in peridotitic suite but also in an extended field of geochemical affinities from high-Ni to low-Ni or maybe even Ni-free environments, such as pyroxenitic or eclogitic.     

Carbon isotopic composition of diamonds from the Archangelsk diamond province

The first data are reported on the carbon isotopic composition of diamond crystals from the Grib pipe kimberlite deposit of the Archangelsk diamond province (ADP). The δ¹³C value of the crystals ranges from ?2.79 to ?9.61‰. The isotopic composition of carbon was determined in three zoned crystals (δ¹³C of ?5.8 ?6.96 ‰, ?5.64/ ?5.85 ‰, and ?5.94/ ?5.69 ‰), two “diamond in diamond” samples (diamond inclusion with δ¹³C of ?4.05 and ?6.34 ‰ in host diamond crystals with δ¹³C of ?8.05 and ?7.54 ‰, respectively), and two samples of coated diamonds (cores with δ¹³C of ?6.98 and ?6.78‰ and coats with δ¹³C of ?7.51 and ?8.01 ‰, respectively). δ¹³C values were obtained for individual diamond crystals from bort-type aggregates (δ¹³C of ?4.24/ ?4.05 ‰, ?6.58/ ?7.48 ‰, and ?5.48/ ?6.08 ‰). Correlations were examined between the carbon isotopic composition of diamonds and their crystal morphology; the color; the concentration of nitrogen, hydrogen, and platelet defects; and mineral inclusions content. It was supposed that the observed δ¹³C variations in the crystals are most likely related to the fractionation of carbon isotopes rather than to the heterogeneity of carbon sources involved in diamond formation. The isotopic characteristics of diamonds from the Grib pipe were compared with those of previously investigated diamonds from the Lomonosov deposit. It was found that diamonds from these relatively closely spaced kimberlite fields are different; this also indicates the existence of spatially localized peculiarities of isotope fractionation in processes accompanying diamond formation.     

The transformation features of impurity defects in natural diamonds of various habits under high <Emphasis Type="Italic">P</Emphasis>–<Emphasis Type="Italic">T</Emphasis> conditions

The results of the investigations of the transformation of impurity defects in natural diamonds of various habits at the stage of high-temperature annealing at P = 6 GPa and T = 2200°C are presented. The studies conducted allowed us to ascertain that the transformations of Aand B-defects in diamonds of octahedral and cubic habits follow general regularities. This fact shows that most of the diamonds of cubic habit with low degree of aggregation of nitrogen centers were not really annealed over a long-term interval. Unlike octahedral diamonds, those of cubic habit are characterized by a pronounced increase in the peak of H-containing defects (3107 cm^–1) after annealing.     

Directional chemical variations in diamonds showing octahedral following cuboid growth

A progression from cuboid to octahedral growth has been observed in 16 natural diamonds from Yakutian kimberlites. X-ray and cathodoluminescence topography have revealed that the change in morphology of diamonds with cloudy cuboid cores may occur without mixed-habit growth but via generation of numerous octahedral apices on cuboid surfaces and subsequent gradual transformation into regular octahedral morphology. Nitrogen aggregation in both cuboid and octahedral domains of such diamonds suggests that they have had a long residence time under mantle conditions. Micro-inclusions in the cuboid domains of the diamonds testify to the nucleation and growth of cuboid cores from a hydrous-carbonatitic (oxidized) fluid. The transition from cuboid hummocky growth rich in inclusions to octahedral growth without inclusions may be linked to decreasing supersaturation in the parent fluid. Measurements of δ¹³C and N_ppm by ion microprobe show that the chemical variations observed between inner cuboid domains and outer octahedral zones commonly have a systematic character and as such they are probably not due to purely kinetic effects. The peripheral octahedral zones are always enriched in ¹³C in comparison with inner cuboid ones, and the total nitrogen content decreases with the change from cuboid to octahedral growth. The octahedral outer zones show a gradual progressive increase in δ¹³C, with an overall change of up to 5‰ from the cuboid core (δ¹³C usually between −8 and −6‰) to the diamond margin (δ¹³C usually between −4 and −2‰). Decreases in δ¹³C of this magnitude with a gradual increase in ¹³C may be attributed to the Rayleigh fractionation operating on a single parent fluid of close to normal mantle δ¹³C composition with diamond precipitating by the reduction of carbonatitic fluid in a closed system. However, one sample shows a variation of δ¹³C of approximately −17 to −6‰ and therefore suggests a possible change of fluid source composition from one containing subducted crustal organic carbon to one with common mantle carbon. An erratum to this article can be found at     

New FTIR spectroscopy data on the composition of the medium of diamond crystallization in metamorphic rocks of the Kokchetav Massif

A representative sample of microdiamonds in calc-silicate and garnet-pyroxene-quartz rocks and gneisses from the cross section of an adit driven at the Kumdy-Kol’ deposit (Northern Kazakhstan) has been analyzed. Microdiamonds from these rocks were studied by Fourier-transform infrared spectroscopy for the first time. It has been established that nitrogen impurity content (300–3000 ppm) and nitrogen aggregation degree (14–75%) vary widely and do not correlate with each other. The variation is probably due to the uneven distribution of nitrogen in crystals and to their specific internal structures.The results of the study show that in most diamondiferous rocks, diamonds crystallized from a fluid/melt of composition varying between aqueous-carbonate and aqueous-silicate end-members. Spectroscopy studies partly disagree with literature data on individual nanoinclusions in diamonds. The cause of this discrepancy may be the evolution of the fluid/melt during diamond crystallization.     

The first finding of graphite inclusion in diamond from mantle rocks: The result of the study of eclogite xenolith from Udachnaya pipe (Siberian craton)

A xenolith of eclogite from the kimberlite pipe Udachnaya–East, Yakutia Grt+Cpx+Ky + S + Coe/Qtz + Dia + Gr has been studied. Graphite inclusions in diamond have been studied in detail by Confocal Raman (CR) mapping. The graphite inclusion in diamond has a highly ordered structure and is characterized by a substantial shift in the band (about 1580 cm^–1) by 7 cm^–1, indicating a significant residual strain in the inclusion. According to the results of FTIR spectroscopic studies of diamond crystals, a high degree of nitrogen aggregation has been detected: it is present mainly in form A, which means an “ancient” age of the diamonds. In the xenolith studied, the diamond formation occurred about 1 Byr, long before their transport by the kimberlite melt, and the conditions of the final equilibrium were temperatures of 1020 ± 40°C at 4.7 GPa. Thus, these graphite inclusions found in a diamond are the first evidence of crystallization of metastable graphite in a diamond stability field. They were formed in rocks of the upper mantle significantly below (≥20 km) the graphite-diamond equilibrium line.     

Fe–S melt as a likely solvent of diamond under mantle conditions

The first results of experimental study of diamond dissolution in a S-bearing Fe melt at high P–T parameters are reported and the morphology of partially dissolved crystals is compared with that of natural diamonds. Our results show that under the experimental conditions (4 GPa, 1400°C), flat-faced octahedral diamond crystals are transformed into curve-faced octahedroids with morphological features similar to those of natural diamonds.     

Н2О as a Possible Initiator of Surface Graphitization of Impact Diamonds

Doklady Earth Sciences - The experimental results on etching of diamond crystals with octahedral and cubooctahedral habits at a temperature of 1000°С in wet argon are presented. It is...     

Distribution of structural impurities and fluid microinclusions in cubic and coated diamond crystals from the Udachnaya pipe,Yakutia, Russia

FTIR microspectroscopic data were used to construct two-dimension maps showing the distribution of structural impurities and mineral microinclusions in cubic and coated octahedral diamond crystals from the Udachnaya kimberlite pipe in Yakutia. Elevated concentrations of hydrogen and total nitrogen are detected in parts corresponding to the early growth of single-episode growth regions of diamond crystals. These concentrations decrease toward the peripheral portions of these regions. The microinclusions contain water and polyphase mineral associations that preserve a high residual pressure. Microinclusions in the coats of octahedral diamond crystals are dominated by silicates, in which the intensity of IR spectral bands increases toward the peripheries, whereas the cubes posses irregularly distributed domains rich in these phases. The carbonate phases of the microinclusions are distributed according to growth zones of the crystals, and their distribution is often not correlated with the concentrations of structural impurities. The facts that microinclusions in the diamond cuboids are dominated by carbonates and that the rims of the octahedra are dominated by silicates suggest that the diamonds crystallized from dominantly carbonate and silicate fluids/ melts, respectively. The chemical composition of the microinclusions point to an eclogitic paragenesis of the crystals. Facts are obtained that provide support for the earlier hypothesis that cubic diamond crystals and coated octahedral crystals grow at metasomatic interaction between deep fluids and eclogitic rocks in the lithospheric mantle.     

Platelet development in cuboid diamonds: insights from micro-FTIR mapping

Fourier transform infrared mapping of diamonds can reveal detailed information on impurities, with a spatial context. We apply this technique, combined with in situ isotopic analysis of carbon, to the study of cuboid diamond growth in a sample that exhibits some mixed-habit growth. While there has been some uncertainty in the literature regarding sectoral differences in nitrogen aggregation and subsequent platelet development, the data from this study appear far more conclusive. We show that despite nitrogen being concentrated in octahedral sectors, there is no detectable difference in the concentration-adjusted rate of nitrogen aggregation within octahedral and cuboid sectors. However, the resultant platelet development is significantly reduced in cuboid sectors compared to contemporaneously formed octahedral sectors. This finding has significant implications for the classification of diamonds using the relationship between their platelet intensity and the absorption caused by B centres. It means that cuboid diamonds naturally fall below the linear relationship that has been termed regular, which would lead to them being incorrectly interpreted as having experienced heating or deformation. The data also support earlier suggestions that large hydrogen concentrations in the diamond-forming fluid may be required for cuboid growth. We further suggest that high nitrogen and hydrogen concentrations are required for mixed-habit diamond growth, which might be the product of specific fluid chemistries that occur in reducing mantle environments.     

The relationship between the distribution of nitrogen impurity centres in diamond crystals and their internal structure and mechanism of growth

Fifty diamond crystals of different morphological types (octahedra, dodecahedroids, cubes and single tetrahexahedroid) with differing internal structures were examined using methods of cathodoluminescence (CL), anomalous birefringence and local infrared (IR) analysis. The main objective of the study was to examine the regularities of nitrogen impurity distribution in diamond with differing internal structures. Almost all the analyzed octahedra, as well as dodecahedroids with zonal structures and the blocky dodecahedroids, are characterized either by nearly isothermic growth conditions or by a decrease in formation temperature during the crystallization process. In contrast to zoned octahedra and dodecahedroids, dodecahedroids with zonal–sectorial and sectorial internal structures show a notably different distribution of nitrogen defects, with N_tot generally decreasing from crystal cores to marginal areas, and degree of nitrogen aggregation increasing in the same direction. From this, it would follow that in these crystals, the temperature of diamond formation of the outer crystal zones is approximately 40–50 °C higher than that of the inner zones. The same result (15 to 80 °C) was obtained for diamond crystals with cubic habit, which generally show a fibrous internal structure, reflecting normal mechanisms of growth. The anomalous distribution of nitrogen centres in diamond crystals that grew through the normal mechanism, with a high rate of growth and in an oversaturated medium, might point to non-equilibrium relationships between the concentrations of different nitrogen centres. It is likely that in crystals of this type, the rate of growth is higher than the rate of structural nitrogen aggregation. Thus, it appears that in these peculiar crystals of diamond we deal with non-equilibrium concentrations of nitrogen B centres and, consequently, with anomalous, non-actual diamond formation temperatures.     

On the possibility of a kinetic fractionation of nitrogen stable isotopes during natural diamond growth

In a diamond from New South Wales (Australia), cubic and octahedral growth sectors, as identified by cathodoluminescence (CL), show slight differences in N-contents of 29 and 42 ppm respectively but no significant differences in either δ¹³C, δ¹⁵N and nitrogen aggregation state with values at +1.96‰, +19.4‰, and 25% Type IaAB aggregation, respectively.Two gem cubes from the Orapa kimberlite (Botswana) were studied by CL revealing a nonfaceted cubic growth. Accordingly, nine other gem cubes were combusted and yielded δ¹³C-values from -5.33‰ to -6.63‰, δ¹⁵N from -1.0‰ to -5.5‰, and nitrogen contents from 914 to 1168 ppm, with nitrogen aggregation state being only Type IaA (zero % B). The gem cubes show striking similarities to fibrous/coated diamonds, not only in both δ¹³C ranges (less than 3‰ from -5 to -8‰), but also in the high levels of nitrogen (≈ 1000 ppm), suggesting that the two diamond types are related. Additionally, no δ¹⁵N variation was detected between the cube and octahedral growth sectors of the Australian diamond, in the cube sectors of the nine gem cubes from Botswana, nor in fibrous/coated diamonds previously studied. These analyses contrast with an earlier study on a synthetic diamond, which reported a strong kinetic fractionation of N-isotopes of about 40‰ between cube and octahedral growth. The present evidence, therefore, suggests that kinetic fractionation of N-isotopes does not operate during natural diamond formation.     

Structural defects in natural plastically deformed diamonds: Evidence from EPR spectroscopy

Structural defects formed as a result of plastic deformation in natural diamond crystals have been studied by EPR spectroscopy. The spectra of brown, pink-brown, black-brown, pink-purple, and gray plastically deformed diamonds of type Ia from deposits in Yakutia and the Urals were recorded. The results of EPR spectroscopy allowed us to identify various deformation centers in the structure of natural diamonds and to show that nitrogen centers were transformed under epigenetic mechanical loading. Abundant A centers, consisting of two isomorphic nitrogen atoms located in neighboring structural sites, were destroyed as a result of this process to form a series of N1, N4, W7, M2, and M3 nitrogen centers. Such centers are characterized by an anisotropic spatial distribution and a positive charge, related to the mechanism of their formation. In addition, N2 centers (probably, deformation-produced dislocations decorated by nitrogen) were formed in all plastically deformed diamonds and W10 and W35 centers (the models have not been finally ascertained) were formed in some of them. It has been established that diamonds with various types of deformation-induced color contain characteristic associations of these deformation centers. The diversity of associations of deformation centers indicates appreciable variations in conditions of disintegration of deep-seated rocks, transfer of diamonds to the Earth’s surface, and formation of kimberlitic deposits. Depending on the conditions of mechanical loading, the diamond crystals were plastically deformed by either dislocation gliding or mechanical twinning. Characteristic features of plastic deformation by dislocation gliding are the substantial prevalence of the N2 centers over other deformation centers and the occurrence of the high-spin W10 and W35 centers. The attributes of less frequent plastic deformation by mechanical twinning are unusual localization of the M2 centers and, in some cases, the N1 centers in microtwinned lamellae. Numerous data on models of deformation centers in natural diamonds, including the M2 and M3 centers, which were observed in the studied collection for the first time, are discussed.     

Enigmatic diamonds in Archean calc-alkaline lamprophyres of Wawa, southern Ontario, Canada

A suite of 80 macrodiamonds recovered from volcaniclastic breccia of Wawa (southern Ontario) was characterized on the basis of morphology, nitrogen content and aggregation, cathodoluminescence (CL), and mineral inclusions. The host calc-alkaline lamprophyric breccias were emplaced at 2.68–2.74 Ga, contemporaneously with voluminous bimodal volcanism of the Michipicoten greenstone belt. The studied suite of diamonds differs from the vast majority of diamond suites found worldwide. First, the suite is hosted by calc-alkaline lamprophyric volcanics rather than by kimberlite or lamproite. Second, the host volcanic rock is amongst the oldest known diamondiferous rocks on Earth, and has experienced regional metamorphism and deformation. Finally, most diamonds show yellow-orange-red CL and contain mineral inclusions not in equilibrium with each other or their host diamond. The majority of the diamonds in the Wawa suite are colorless, weakly resorbed, octahedral single crystals and aggregates. The diamonds contain 0–740 ppm N and show two modes of N aggregation at 0–30 and 60–95% B-centers suggesting mantle storage at 1,100–1,170°C. Cathodoluminescence and FTIR spectroscopy shows that emission peaks present in orange CL stones do not likely result from irradiation or single substitutional N, in contrast to other diamonds with red CL. The diamonds contain primary inclusions of olivine (Fo₉₂ and Fo₈₉), omphacite, orthopyroxene (En₉₃), pentlandite, albite, and An-rich plagioclase. These peridotitic and eclogitic minerals are commonly found within single diamonds in a mixed paragenesis which also combines shallow and deep phases. This apparent disequilibrium can be explained by effective small-scale mixing of subducted oceanic crust and mantle rocks in fast “cold” plumes ascending from the top of the slabs in convergent margins. Alternatively, the diamonds could have formed in the pre-2.7–2.9 Ga cratonic mantle and experienced subsequent alteration of syngenetic inclusions related to host magmatism and ensuing metamorphism. Neither orogenic nor cratonic model of the diamond origin fully explains all of the observed characteristics of the diamonds and their host rocks. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

The Effect of Aggregation of Impurity Nitrogen on Diamond X-Ray Luminescence

Two samplings of 65 diamond crystals divided by the intensity of a slow X-ray luminescence component are studied from the Arkhangel’skaya and Karpinskogo-1 pipes. IR and EPR spectroscopies revealed a relationship between the nitrogen A and P2 centers of the diamonds and the presence of a slow X-ray luminescence component. Its absence in most diamonds with high content of P1 (C) centers is explained by the low number of A and P2 centers.