THEMED ISSUE: Ophiolites, Diamonds, and UHP Minerals: New Discoveries and Concepts on Upper Mantle Petrogenesis

Spectroscopic analysis of microdiamonds in ophiolitic chromitite and peridotite

Kyaw Soe Moe1, Jing-Sui Yang2, Paul Johnson1, Xiangzhen Xu2, and Wuyi Wang1 1GEMOLOGICAL INSTITUTE OF AMERICA, 50 W 47TH STREET, NEW YORK, NEW YORK 10036, USA 2STATE KEY LABORATORY OF CONTINENTAL TECTONICS AND DYNAMICS, CENTER FOR ADVANCED RESEARCH ON MANTLE (CARMA), CHINESE ACADEMY OF GEOLOGICAL SCIENCES, 26 BAIWANZHUANG ROAD, BEIJING, 100037, CHINA

ABSTRACT

Microdiamonds ~200 µm in size, occurring in ophiolitic chromitites and peridotites, have been reported in recent years. Owing to their unusual geological formation, there are several debates about their origin. We studied 30 microdiamonds from 3 sources: (1) chromitite ore in Luobusa, Tibet; (2) peridotite in Luobusa, Tibet; and (3) chromitite ore in Ray-Iz, polar Ural Mountains, Russia. They are translucent, yellow to greenish-yellow diamonds with a cubo-octahedral polycrystalline or single crystal with partial cubo-octahedral form. Infrared (IR) spectra 0 revealed that these diamonds are type Ib (i.e., diamonds containing neutrally charged single substitutional nitrogen atoms, Ns, known as the C center) with unknown broad bands observed in the one-phonon region. They contain fluid inclusions, such as water, carbonates, silicates,

hydrocarbons, and solid CO2. We also identified additional microinclusions, such as chromite, magnetite, feldspar (albite), moissanite, hema- tite, and magnesiochromite, using a Raman microscope. Photoluminescence (PL) spectra measured at liquid nitrogen temperature suggest that these diamonds contain nitrogen-vacancy, nickel, and H2 center defects. We compare them with high-pressure–high-temperature (HPHT) synthetic industrial diamond grits. Although there are similarities between microdiamonds and HPHT synthetic diamonds, major differences in the IR, Raman, and PL spectra confirm that these microdiamonds are of natural origin. Spectral characteristics suggest that their geological formation is different but unique compared to that of natural gem-quality diamonds. Although these microdiamonds are not commercially important, they are geologically important in that they provide an understanding of a new diamond genesis.

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INTRODUCTION of these diamonds, and propose no model of detector was used to collect IR spectra. The formation. spectra for each sample are collected with 1 cm–1 During recent years, yellow cubo-octahedral spectral resolution and 100 × 100 µm aperture diamonds ranging from 0.2 to 0.5 mm have been MATERIALS AND METHODS size from 700 to 4000 cm–1 spectral range for discovered in ophiolitic chromitite and perido- 256 scans. We tested for possible contamina-

tite deposits in Tibet and the polar Ural Moun- Sizes of microdiamonds in this study range tions, such as moisture and CO2 in the FTIR tains (Polar Urals; Yang et al., 2014). Models from 200 to 250 µm in width (Fig. 1). Most system and for grease on the glass slide. By of formation for these new sources have been of the microdiamonds are crystal fragments, measuring the IR spectrum of a gem-quality proposed by many (Yang et al., 2014, 2015; containing cubo-octahedral facets. They were type IIa diamond (i.e., contains no detectable Howell et al., 2015; Robinson et al., 2015; discovered in Luobusa and Ray-Iz ophiolites nitrogen defects using FTIR) with the same con- Xiong et al., 2015; Xu et al., 2015; Griffin et (Fig. 2). We examined 30 samples: 10 from Luo- ditions of collection for the microdiamonds, we al., 2016). However, their unusual geological busa chromitite, 10 from Luobusa peridodite, eliminated the possibility of such errors. occurrence and appearance, similar to industrial and 10 from Ray-Iz chromitite. We also col- We used a Renishaw inVia Raman micro- HPHT synthetic diamond grits, have raised con- lected spectra for 10 yellow HPHT synthetic scope to measure Raman and photolumines- cerns among many researchers, who have tried industrial diamond grits with sizes ranging from cence (PL) spectra. The Raman spectra for to prove, using a variety of methods, that these 250 to 300 µm; they are from an unknown manu- inclusions were collected with a range from diamonds occur in nature. facturer and are compared with microdiamonds. 100 to 1200 cm–1 at room temperature, using We studied microdiamonds found in Luo- All samples were cleaned in an ultrasonic cleaner 514.5 and 830.0 nm lasers. The laser spot sizes busa (Tibet) and Ray-Iz (Polar Urals) ophiol- with acetone, then cleaned again with deionized of the 514.5 nm and 830.0 nm lasers (using ites using Fourier transform infrared (FTIR) and water in ultrasonic cleaner. Subsequently, the a Leica 50x objective) are 1.14 and 1.84 µm, Raman microscopy. We have characterized their samples were heated at 70 °C for 30 min to respectively. PL spectra were measured with diamond type, inclusions, and defects. Our goal remove moisture. 514.5, 632.8, and 830.0 nm laser excitations is to identify the origin of these diamonds, and The Thermo Scientific Nicolet iN 10 FTIR- at liquid nitrogen temperature. Samples were determine if they are of natural or synthetic ori- microscope with an attached liquid nitrogen– submerged in the liquid nitrogen double-layer gin. We have solely focused on the identification cooled MCT (mercury-cadmium-telluride) bath method.

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syngenetic inclusions represent the composition of diamond-forming fluids, containing water and carbonates as the main volatile components. Water and carbonates were first observed in cuboid diamonds using FTIR by Chrenko et al. (1967). Mantle-derived fluids (or volatile-rich melt) can be trapped as homogeneous, high- density fluids. During ascending and cooling, fluid inclusions are formed as a secondary phase (i.e., the separation of immiscible fluids), and low-density fluids can be trapped inside them. FTIR is a useful tool to study such fluid inclu- sions, and it can also measure the bulk content.

Water The presence of water is confirmed by broad peaks with various positions from 3286 to 3377 cm–1 (OH stretching; Fig. 3) and a peak at ~1740 –1 cm (H2O bending; Fig. 3) observed in all micro- Figure 1. Mosaic image of microdiamonds obtained from three locations. Scale bars = 20 µm. (A–D) diamonds studied. The 1740 cm–1 peak is associ- Ray-Iz chromitite. (E–H) Luobusa chromitite. (I–L) Luobusa peridotite. ated with a 1660 cm–1 peak at its shoulder. Water has been reported in fibrous and coated cuboid diamonds (De Corte et al., 1998; Kagi et al., 2000; Zedgenizov et al., 2006; BenDa- vid et al., 2007; Kopylova, 2010). Water can be observed as hydroxyl groups inside fibrous diamonds. Thus, diamond can carry hydrous components directly from the Earth’s mantle. Kagi et al. (2000) showed evidence for water as solid inclusions in the form of ice VI (i.e., high- pressure form of water) inside cuboid diamonds.

Hydrocarbons IR spectra confirm the presence of hydro- carbon peaks in the microdiamonds (Fig. 3). All these peaks are slightly broad and they are located approximately at 2854, 2872, 2925, and 2958 cm–1. A peak at 2854 cm–1 is caused by symmetric stretching, and a peak at 2925 cm–1

is caused by asymmetric stretching of CH2

hydrocarbons (Titus et al., 2005). CH3 hydro- carbons contribute to the symmetric and asym- metric stretching bands at 2880 and 2960 cm–1, respectively (Titus et al., 2005). However, we do Figure 2. Microdiamonds in this study are found in Ray-Iz ophiolites in Russia (inset) and Luobusa not observe individual hydrocarbon inclusions ophiolites in Tibet (after Yang et al., 2014). under the Raman microscope, suggesting that they are fluid inclusions of <1 µm. Hydrocarbon fluid inclusions of ~20 µm have been reported in natural diamonds from RESULTS AND DISCUSSION Inclusions Identified by FTIR Spectra placers of Yakutia, Russia (Tomilenko, 2008). The Raman and IR spectroscopy confirms the

Optical Characteristics and Surface The diamond intrinsic absorption band existence of water-nitrogen-hydrocarbon (CH4- Features observed in the IR spectrum confirms that these rich) high-density fluids in these diamonds. samples are diamond (Fig. 3); it also reveals the Tomilenko (2008) proposed that hydrocarbons The microdiamonds are yellow to greenish- presence of water, hydrocarbons, carbonates, sili- are the source of carbon as well as carbon car-

yellow, semitransparent to translucent, and both cates, and solid CO2 (Fig. 3). The fluid inclusions riers during diamond formation; however, this polycrystalline and single crystal diamonds can are nanometer-sized (<1 µm) solid phases inter- theory is still debated. be observed. The surfaces have etch features, grown with minor amounts of hydrous solution Hydrocarbons have also been reported in similar to step-like markings, usually found on and gas bubbles (Kopylova, 2010). They were fibrous cuboid diamonds from the Democratic natural rough diamonds (Fig. 1). trapped during the diamond formation. These Republic of the Congo (Kopylova, 2010). It

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has been proposed that hydrocarbons occurred

by deuteric reaction between trapped CO2 and hydrogen, released from the formation of sec- ondary OH-bearing minerals. The intensity of hydrocarbon peaks in cuboid diamonds is much stronger than OH-stretching bands, very similar to hydrocarbons bands observed in our samples. The hydrocarbon peaks, OH-stretching, and car- bonate bands show a positive correlation consis- tent with that of natural formation of diamond.

Carbonates All of the microdiamonds contain a carbon- ate peak at ~1460 cm–1, which is an asymmetric stretching band (Fig. 3). The abundance of car- bonate fluid inclusions suggests that carbonatitic high-density fluids are involved in the diamond growth process. Zedgenizov et al. (2004) pro- posed that diamond growth was caused by pre- cipitation of free carbon in carbonatitic melt or through carbonate-silicate interaction. The abundance of carbonate fluid inclusions inside natural diamond is well known. There are many detailed studies about carbonate inclu- Figure 3. Infrared (IR) spectra of microdiamonds. (A) Fluid inclusions of water, hydrocarbon, carbon- sions (e.g., De Corte et al., 1998; Zedgenizov ate, and silicate are shown. Arrows indicate various peak positions of water (OH stretching). The solid et al., 2004, 2006). –1 CO2 was not shown here. (B) Detailed IR spectral region from 700 to 1800 cm : water (H2O bend- ing) at 1740 cm–1 and its associated peak at 1660 cm–1, carbonate and silicate inclusions, nitrogen Silicates defects, and unknown peaks. Spectra are normalized and vertically shifted for clarity. a—Luobusa Silicate peaks are detected at 967 and 1085 chromitite; b—Luobusa peridotite; c—Ray-Iz chromitite. cm–1 in all of the microdiamonds studied (Fig. 3). Silicate fluid inclusions have been previously discovered in cuboid and fibrous-coated dia- in the microdiamonds are located at even higher monds (Yelisseyev et al., 2004; Zedgenizov et positions at 2513 and 3687 cm–1, possibly al., 2004; BenDavid et al., 2007). In the diamond caused by intense internal pressure. The pres- stability field, silicate, carbonatitic, and hydrous sure during diamond formation can be much melts and/or fluids are fully miscible, and they higher than the internal pressure measured at can be trapped inside diamond as highly con- room temperature (Schrauder and Navon, 1993). centrated fluids. Sheet silicates can be formed Evidence of high internal pressure suggests that as secondary minerals from the trapped fluids. fluid inclusions have been trapped during dia- The presence of silicates is further confirmed mond growth. by the discovery of two feldspar inclusions in Ray-Iz diamonds (discussed in the following). Inclusions Identified by Raman Spectra

Solid CO2 We identified 22 microinclusions, with sizes Figure 4. Infrared (IR) spectra of a few microdi-

Carbon dioxide is the most abundant vola- ranging from 5 to 20 µm, using a Raman micro- amonds showing solid CO2 inclusion. Spectra tile component in the Earth’s mantle (Schrauder scope. They are chromite, magnetite, feldspar are vertically shifted for clarity. a—Luobusa chro- and Navon, 1993). Solid CO inclusion can be (albite), moissanite, hematite, and magnesio- mitite; b and c—Ray-Iz chromitite; d—Luobusa 2 peridotite; ACO —atmospheric CO at 2365 cm–1. observed in a few samples, two from Luobusa chromite (Table 1). Most of them are individual 2 2 (chromitite), three from Luobusa (peridotite), inclusions, but a few are nontouching monomin- and four from Ray-Iz (Fig. 4). The peaks at eralic or polymineralic assemblages (Table 2). TABLE 1. LIST OF IDENTIFIED MICROINCLUSIONS 2375, 2513, 3687, and 3748 cm–1 are related All of the inclusions are located below the sur- to solid CO . Natural diamonds containing this face, with the exception of one of seven chro- Inclusions Luobusa Luobusa Ray-Iz 2 chromitite peridotite chromitite fluid inclusion have been reported previously. mite inclusions and a hematite inclusion that Schrauder and Navon (1993) discovered solid break on the surface. We also observed multiple chromite 025 magnetite121 CO2 in a brownish-yellow diamond. The IR inclusions of <1 µm under the Raman micro- feldspar 002

spectrum revealed solid CO2 peaks at 650 (v2), scope. Since they are smaller than laser spot size, moissanite 411 hematite 010 2376 (v3), 3620 (v3 + 2v2), and 3752 (v3 + v1) we cannot identify them. However, the identifi- cm–1. These are shifted toward higher peak posi- cation of 22 inclusions in these microdiamonds magnesiochromite2 00 tions from one atmosphere pressure, caused by is important, providing strong evidence of the Note: this shows the total number of inclusions internal pressure of 5 GPa. The peaks observed natural origin. observed in each location.

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TABLE 2. INCLUSIONS OBSERVED IN INDIVIDUAL DIAMONDS Sample Inclusions KCr2 moissanite KCr3 moissanite KCr5 magnesiochromite, magnesiochromite KCr6 moissanite KCr7 moissanite KY2 magnetite KY4 chromite, magnetite, hematite KY6 chromite KY7 magnetite KY9 moissanite WP1 chromite WP11 magnetite WP6 chromite, chromite, chromite WP8 feldspar WP9 feldspar, moissanite WP10 chromite Note: KCr—Luobusa chromitite; KY—Luobusa Figure 5. Raman spectra of peridotite; WP—Ray-Iz chromitite. microinclusions. Inclusions are marked with arrows; the scale bars = 20 µm.

Chromite Raman shifts observed for the translucent to opaque, reddish-orange chromite inclusions are located at 550, 692, and 723 cm–1 (Fig. 5). These are most abundant in Ray-Iz diamonds, but two of them are observed in Luobusa (perido- tite) samples. Most inclusions are single crystals; one Ray-Iz sample contains three chromite inclu- sions. One chromite is associated with magnetite and hematite inclusions in the Luobusa (perido- tite) sample (Table 2). Chromite is a mantle-derived mineral, and it is indicative of peridotitic paragenesis. It has been observed as a macro-inclusion in natural diamonds (McKenna et al., 2004). It can also be found as microinclusions, e.g., ~50 µm inclu- sions in microdiamonds from kimberlites in the Yakutia (Sobolev et al., 2004). Chromite micro- is individual, and the other is associated with Moissanite inclusions have also been observed in fibrous dia- moissanite. Their Raman shifts can be located Gray to black opaque moissanite inclusions monds (Zedgenizov et al., 2004). The composi- at 292, 411, 478, 510, 761, and 817 cm–1 (Fig. are present in diamonds from all three sources. tion of chromite grains obtained from kimberlites 5). Feldspar inclusions, such as sanidine, can However, they are most abundant in the Luo- in central India confirmed that they can occur in be observed in natural diamonds, as reported busa (chromitite) samples. Their Raman peaks the diamond stability field (Mainkar et al., 2004). in Siberian and Venezuelan diamonds (Meyer, are located at 150, 765, 786, and 966 cm–1 1985; Novgorodov et al., 1990; Sobolev et al., (Fig. 5). The Raman spectra indicate that they Magnetite 1998). However, the Raman spectrum of our are most likely 6H SiC crystals. The moissanite We confirmed opaque black crystals as mag- feldspar inclusion is very similar to the refer- is included as single crystals with the exception netite with Raman shifts at 544 and 671 cm–1 ence spectrum of albite. of the Ray-Iz diamond where it is associated (Fig. 5). These are individual inclusions, and one Feldspar, however, is not stable in the dia- with feldspar inclusions (Table 2). crystal is associated with chromite and hematite mond stability field. It can be formed inside Moissanite inclusions can also be observed found in the Luobusa (peridotite) sample. cracks or fractures by secondary fluids. Both in natural diamonds from Western Australia, Magnetite inclusions can be syngenetic and of the feldspar (albite) inclusions in the micro- South Africa, North America, and China (Jaques have been observed in natural diamonds from diamonds are completely enclosed inside the et al., 1989; Moore and Gumey, 1989; Otter and around the world (Gorshkov et al., 1997; Sobo- host diamond. However, we do not observe any Gurney, 1989; Leung, 1990; Gorshkov et al., lev et al., 1998; Titkov et al., 2003; Hayman et healed fractures around them. The time required 1997; Field et al., 2008). Leung (1990) discov- al., 2005; Jacob et al., 2009). to completely enclose an inclusion inside dia- ered three moissanite inclusions in an octahe- mond by fracture healing, i.e., the age of feldspar dral diamond from Fuxian, China. Observed in Feldspar inclusions, would take at least few hundred years one inclusion, 6H SiC crystals were enclosed in Two of the Ray-Iz microdiamonds con- if not thousands of years. The age of feldspar a colorless grain of 3C SiC. Three moissanite tain translucent, gray feldspar inclusions: one is important in our research (discussed herein). inclusions were surrounded by a thin layer of

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glass, which also contained calcium carbonate Magnesiochromite can be observed as abun- These broad bands are possibly masking nitrogen –1 0 –1 and calcium sulfate crystals. Therefore, it was dant inclusions in placer diamonds from Brazil A aggregates at 1282 cm and Ns at 1131 cm concluded that moissanite inclusions originated (Tappert et al., 2006). They are indicative of peri- in some diamonds. from the mantle. dotitic paragenesis, and diamond formation tem- Segregation of Fe-Ni-Si-C alloy liquid can perature can be extrapolated as 1210–​1340 °C Defects Detected by PL Spectra facilitate the crystallization of diamond and/or (Tappert et al., 2006). moissanite in the lower mantle (Dasgupta, 2013). Nitrogen-Vacancy Centers Because moissanite is a highly reduced mineral, Defects Detected by FTIR Spectra Nitrogen-vacancy (NV) centers are detected Leung (1990) proposed that it can occur in geo- at 575 (NV0) and 637 (NV–) nm with broad

logical environments with extremely low fO2 The nitrogen defect (C center) can be detected phonon sidebands ranging from 647 to 804 nm values or conditions at depths >250 km. Thus, at 1344 cm–1 in all samples (Fig. 3). This defect (Fig. 6). The NV– has a higher intensity than the moissanite can be a potential carbon source for can also be detected at 1131 cm–1 in some of the NV0 center. The width of NV centers is slightly diamond formation; therefore, it can be trapped diamonds. The C center–containing diamonds broad with average FWHM (full width at half as inclusions during diamond formation. can be classified as type Ib, and they are very maximum) values of 2.18 nm for NV0 and 2.75 rare in nature (<1% of natural gem-quality yel- nm for NV– centers. Hematite low diamonds). We decided not to measure the Broad NV centers with a similar ratio (637 > A translucent, orange-red hematite crystal concentration of nitrogen because of the pres- 575) and phonon sidebands can be observed in is breaking the surface in a Luobusa (perido- ence of unusual broad bands observed in the one- yellow coated diamonds from Snap Lake–King tite) diamond. It is associated with chromite and phonon region, which may cause potential errors. Lake kimberlites in Canada (Yelisseyev et al., + magnetite crystals. The Raman shifts are located A positively charged nitrogen atom, Ns , at 1332 2004). It has been proposed that strain from at 223, 289, 405, and 608 cm–1 (Fig. 5). cm–1 can be observed in all samples (Fig. 3). nickel-related defects was contributing broad Hematite inclusions are observed in dia- Two peaks at 1365 and 1378 cm–1 are detected NV peaks. We confirmed the presence of nickel- monds from Jericho kimberlites in Canada and in the microdiamonds (Fig. 3). They are similar related defects in our samples by detection of in gray Siberian diamonds (Titkov et al., 2003; to platelet peaks, which can be detected from the 882–884 nm doublet (Fig. 6). Therefore, De Stefano et al., 2009). Hematite inclusions (>5 spectral range 1358 to 1380 cm–1 (Zaitsev, 2001). nickel defects are most likely causing broad NV µm) associated with magnetite were observed in The platelet is a {100} planar defect containing peaks in microdiamonds. The NV centers can be frame sites (i.e., polycrystalline diamond aggre- carbon interstitials and nitrogen atoms (Woods, caused by exposure to postgrowth ionizing irra- gates) from the Orapa Mine in Botswana (Jacob 1986). However, they coexist and are linearly cor- diation with natural low-temperature annealing et al., 2009). Hematite is currently assigned to related with the B center (i.e., nitrogen aggre- (Yelisseyev et al., 2004). The similar NV ratio unknown or uncertain diamond paragenesis. gates) in natural diamonds. The microdiamonds and broad sidebands have also been observed Hematite is not a primary mineral in the mantle, do not show the B center at 1175 cm–1, although in natural ABC (i.e., diamonds containing A, B, and it is possibly formed after low-nickel sul- there are broad peaks at ~1155 and ~1185 cm–1 and C nitrogen centers; A = aggregate of two fides (Szabó and Bodnar, 1995). (Fig. 3). These broad peaks are possibly mask- nitrogen atoms; B = aggregate of four nitrogen ing the B center. Considering this fact and the atoms) and type Ib diamonds (Hainschwang et Magnesiochromite clear nature of the peaks, the 1365 and 1378 cm–1 al., 2006, 2013). Two magnesiochromite inclusions are identi- peaks are most likely attributed to platelet defects. fied in one diamond from Luobusa (chromitite). Additional unknown peaks were also detected Nickel Defect They are translucent, pale orange crystals. at 1209, 1245, 1275, and 1311 cm–1 in the one- Nickel-related peaks at 882 and 884 nm in Raman shifts are located at 529 and 692 cm–1 phonon region, and 1495 cm–1 in the two-pho- diamonds can be observed in diamonds from all (Fig. 5). non region (Fig. 3; some peaks are not shown). sources, but their intensity is source dependent.

Figure 6. Photoluminescence (PL) spectra of microdiamonds and high-pressure–high-temperature (HPHT) synthetic diamond grit. (A) Excited with 514 nm laser at liquid nitrogen temperature (LNT), showing nitrogen-vacancy (NV) centers and phonon sidebands. (B) PL spectra excited by 830 nm laser at LNT. It shows 882–884 nm doublet, H2 center, and peaks at 909 and 953 nm for microdiamonds from chromitite, and 865 and 871 nm peaks for HPHT synthetic diamonds. (C) PL spectra excited by 633 nm laser at LNT. The 657 nm peak is detected in all diamonds. A triplet at 693 nm can be observed in HPHT synthetic diamond. Spectra are normalized and vertically shifted for clarity. a—Ray-Iz chromitite; b—Luobusa peridotite; c—Luobusa chromitite; d—HPHT synthetic diamond; AR—artifact.

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The ratio between the 882 and 884 nm doublet are too small to measure ultraviolet-visible spec- Individual hydrocarbon inclusions in HPHT and diamond Raman peak is reversely related tra. However, the presence of the H2 center is synthetic diamonds were reported by Tomilenko between chromitite and peridotite sources; in confirmed using PL spectroscopy. et al. (1998). They are transparent and color- the Luobusa (chromitite) and Ray-Iz diamonds, less fluid inclusions of 5–40 µm with tabular, they are stronger than the diamond Raman peak 657 Center lenticular, and disc shapes. We did not observe but broad and weak in the Luobusa (peridotite) The 657 nm peak can be observed in all such transparent inclusions in both the microdia- diamonds (Fig. 6). Therefore, microdiamonds micro­diamonds (Fig. 6). This peak has been monds and industrial diamond samples. Instead, from both chromitite sources are nickel rich. reported in natural diamonds (Adams and Payne, we identified submicron hydrocarbon inclusions The nickel defect is commonly observed in 1974), and nickel-rich, type IaA orange-yellow in both microdiamond and HPHT synthetic in HPHT synthetic diamond grown with nickel cat- diamond (Hainschwang and Notari, 2004). the IR spectrum (Fig. 7). Their peaks are located alyst, but it can be rarely seen in natural type Ib at 2958, 2925, 2872, and 2854 cm–1. diamonds. Nickel defects, such as Ni-N com- Unknown Defects After normalizing and comparing the IR spec- plexes, have been reported in yellow coated dia- Additional defects were detected at 909 tra, as shown in Figure 7, the intensity of 1344 monds from Snap Lake–King Lake kimberlites and 953 nm (Fig. 6). These are observed in the cm–1 in HPHT synthetic diamond grit appears in Canada (Yelisseyev et al., 2004). Diamonds nickel-rich Luobusa (chromitite) and Ray-Iz much stronger than in the microdiamonds. The from Siberia, Canada, and Australia may also diamonds, but not in the nickel-poor Luobusa hydrocarbon peaks are weaker in the HPHT syn- contain nickel defects (Yelisseyev et al., 2004). (peridotite) diamonds. Their assignments are thetic grit (Fig. 7). The 882–884 nm doublet can also detected in unknown. natural type Ib diamonds along with the Y center Raman Spectral Analysis defect at 799.4 nm (Hainschwang et al., 2013). Comparison with Industrial Diamond Grits Elongated or irregularly shaped microinclu- Nickel can enhance a faster nitrogen aggre- sions, containing methane, hydrocarbons, car- gation process (Fisher and Lawson, 1998). How- There are three types of diamond used for bon dioxide, water, and amorphous carbon clus- ever, we do not see any clear peaks for A and B drill bits in the oil and gas industry: polycrys- ters, can be found in HPHT synthetic diamonds, aggregates in microdiamonds. Instead, unknown talline diamond compact (PDC), HPHT-grown grown in the Fe-Ni-C system (at 60 kbar and broad bands are observed in the nitrogen spec- synthetic diamond grits (used for grit hot-pressed 1350–1400 °C), and the carbonate-carbon system tral region from 1000 to 1400 cm–1. These broad inserts), and natural bort diamonds. They are (at 70 kbar and 1700–1750 °C) (Tomilenko, 2008). bands are probably masking the A and B centers applied to drill bits without moving parts and These can be detected by Raman spectroscopy. (Fig. 3). are called fixed cutters. HPHT synthetic grits However, we did not observe Raman-active

have similar size and crystal form compared water and CO2-rich microinclusions in both H2 Center to the microdiamonds. Therefore, we decided microdiamonds and HPHT synthetic diamonds. The H2 center defect is detected at 986 nm to examine three HPHT synthetic diamond Instead, we found metallic flux inclusions in the in all microdiamonds (Fig. 6), except a few grits of unknown manufacture using the same HPHT synthetic grits, as reported in previous of them that did not show it. This defect is a instruments and measurement parameters. The studies (Shigley et al., 2004). negatively charged nitrogen-vacancy-nitrogen samples are ~300 µm yellow, cubo-octahedral (N-V-N)– center, and is located along the <110> crystals. PL Spectral Analysis direction (Zaitsev, 2001). NV centers are detected at 575 (NV0) and The H2 center can be observed in natural IR Spectral Analysis 637 (NV–) nm in HPHT synthetic diamonds (Fig. yellow and brown ABC diamonds, and type Ib The C center can be observed at 1130 and 6). NV centers can be observed in irradiated and orange diamonds (Hainschwang et al., 2006 and 1344 cm–1 in HPHT synthetics (Fig. 7). Unlike annealed HPHT synthetic diamonds (Lawson et 2013) in the absorption spectrum. Our samples microdiamonds, both peaks are clearly seen. al., 1998). The ratio of NV centers and phonon

Figure 7. Comparison of microdiamonds and high-pressure–high-temperature (HPHT) synthetic diamond in infrared (IR) spectra. (A) Spectral range from 800 to 1800 cm–1 shows nitrogen defects, water, carbonate, and silicate. a—Luobusa chromitite; b—Luobusa peridotite; c—Ray-Iz chromitite; d—HPHT synthetic diamond. (B) Spectral range from 2700 to 4000 cm–1 shows hydrocarbon and water peaks. Spectra are normalized and vertically shifted for clarity. a–d are the same as in A. (C) Comparison of IR spectrum of microdiamond with spectra of gem-quality type IIa diamond, and glass slide. a— Ray-Iz chromitite microdiamond; b—gem-quality diamond; c—glass slide.

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The microdiamonds were placed on a glass slide to measure spectra. We also collected the IR spectrum of the glass slide and it showed a flat line, with only two broad peaks at 816 and 1271 cm–1 (Fig. 7). These broad peaks are not observed in any of the microdiamonds. Using this confirmation, we can conclude that the IR absorption peaks of fluid inclusions are real, and not caused by contamination from either the samples or the FTIR system.

Cubo-octahedral and Dodecahedroid Form

The microdiamonds are cubo-octahedral polycrystalline crystals or single crystals with partial cubo-octahedral form, with the exception of one Luobusa (peridotite) diamond that shows flat dodecahedroid form (Fig. 8). Cubo-octahedral diamonds have been reported in nature. Diamonds from the Swartruggens dike in the Helam Mine, South Africa, exhibit cubo- octahedral growth sectors (McKenna et al., 2004). Octahedral diamonds from Yakutian kimberlites have cubo-octahedral growth bands (Bulanova, 1995). This growth pattern can also be observed Figure 8. Mosaic image of crystal habit of microdiamonds. Scale bar for F is 200 µm; for all other in natural gem-quality diamonds, suggesting that images, scale bar is 20 µm. (A–C) Cubo-octahedral polycrystalline form, Ray-Iz diamonds. (D) Partial cubo-octahedral form, Ray-Iz diamond. (E) Luobusa (peridotite) diamond. (F) Dodecahedroid form, diamonds are essentially crystallized as cubo- Luobusa (peridotite) diamond. (G) Luobusa (peridotite) diamond. (H, I) Luobusa (chromitite) diamonds. octahedra in the early stages of formation. Cubo-octahedral inclusions are frequently observed in natural diamonds. Cubo-octahedral sidebands in HPHT synthetic diamond grits look (Shigley et al., 2004). It can also be observed magnetite grains of 10–60 µm can be observed similar to those observed in both microdiamond in natural diamonds (Adams and Payne, 1974; in lower mantle diamonds from Rio Soriso in and natural diamond. Hainschwang and Notari, 2004). Brazil (Hayman et al., 2005). These diamonds Nickel defects can be detected at the 882 Peaks at 565, 865, and 871 nm, and the 693 also have cubo-octahedral growth sectors, indic- and 884 nm doublet (Fig. 6). The intensity is nm system (691-692-693 triplet; Fig. 6) are ative of lower crystallization temperatures com- much weaker compared to microdiamonds from also observed in HPHT synthetic diamond grits. pared to octahedral diamonds. chromitite sources. Nickel alloy has been widely However, none of these peaks were detected Although most natural diamonds crystallize used in growing commercial HPHT synthetics. in microdiamonds. The 565 nm peak is com- in the octahedral form, some diamonds may Consequently, single nickel atoms (most likely monly observed in natural, gem-quality type Ib have cuboid or cube or complex growth forms. interstitial Ni+) can be introduced into the dia- diamonds. The assignments of aforementioned Cuboid-octahedral diamonds, along with cubes mond lattice in {111} growth sectors during peaks are unknown. and other unusual shapes from the Jwaneng HPHT synthesis (Collins, 2000). Nickel defects Mine in Botswana were reported by Welbourn can be observed in HPHT synthetic diamond, Possible Contamination et al. (1989). Natural cubo-octahedral diamonds which is grown in Fe-Ni-C system and annealed were discovered from ultramafic belts of Arme- above 1700 °C (Yelisseyev et al., 2004). Samples were cleaned by soaking in acetone nia (Pavlenko et al., 1974). De Corte et al. (1998) The H2 center is detected at 986 nm (Fig. 6). for 30 min, and air-dried for another 30 min. reported and analyzed 16 ~200–380 µm cubo- The intensity is higher than the diamond Raman After observing strong hydrocarbon and water octahedral alluvial diamonds from the Kokchetav peak. This center can be produced by irradia- peaks in the IR spectra, we suspected a possible massif, northern Kazakhstan. Four cubo-octahe- tion and annealing at ~1700 °C in type Ib syn- contamination of the samples. We performed dral diamonds were found in the Swartruggens thetic diamonds (Mita et al., 1990). This defect additional cleaning using acetone and deionized dike in the Helam Mine, South Africa (McKenna is observed in microdiamonds from all three water inside ultrasonic cleaner. We then dried et al., 2004). Cubo-octahedral diamonds can be sources (Fig. 6). However, the H2 peak has rela- the samples with a low heat. formed at intermediate growth rates, between tively higher intensity in synthetic diamond than In order to confirm that the FTIR micro- the low growth rate of octahedra and the high in the microdiamonds. Natural diamonds can scope system was working properly, we tested a growth rate of cubes. also contain the H2 defect (Hainschwang et al., gem-quality, type IIa diamond parallel to mea- One of the diamonds from the Luobusa (peri- 2006, 2013). suring microdiamonds. The IR spectrum of the dotite) shows a flat dodecahedroid form (Fig. 8). The 657 nm peak can be observed in HPHT gem-quality diamond did not show hydrocarbon, Dodecahedroid diamonds can be found in nature. synthetic diamonds, as well as in microdiamonds water, and other fluid-inclusion peaks (Fig. 7). Five dodecahedroid diamonds were discovered (Fig. 6). This peak was reported in Chatham syn- When we resumed measuring IR spectra for in Yakutian kimberlites (Bulanova, 1995). One thetic diamonds, and attributed to nickel defects microdiamonds, these peaks appeared again. of them is a flat dodecahedroid, similar to the

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diamond shown in Figure 8. Initial cubic growth 50 yr ago. Based on the finding of feldspar inclu- and Petrology, v. 158, p. 295–315, doi:​10​.1007​/s00410​ -009​-0384​-7. can be transformed into dodecahedron form in sions, which are at least a few hundred years old, Field, M., Stiefenhofer, J., Robey, J., and Kurszlaukis, S., 2008, the later stages of crystallization (Bulanova, in conjunction with additional microinclusions Kimberlite-hosted diamond deposits of southern Africa: 1995). Dodecahedroid diamonds can also be of older ages, we can conclude that microdia- A review: Ore Geology Reviews, v. 34, p. 33–75, doi:10​ ​ .1016​/j​.oregeorev​.2007​.11​.002. found in alluvial deposits from the ultramafic monds did not originate from drill bits. Fisher, D., and Lawson, S., 1998, The effect of nickel and co- belts of Armenia (Pavlenko et al., 1974). balt on the aggregation of nitrogen in diamond: Diamond CONCLUSION and Related Materials, v. 7, p. 299–304, doi:10​ .1016​ /S0925​ ​ -9635​(97)00246​-X. Natural versus Synthetic Origin: Why They Gorshkov, A.I., Bao, Y.N., Bersho, L.N., Ryabchikov, I.D., Cannot Have Originated from Drill Bits The microdiamonds from Luobusa and Ray- Sivtsov, A.V., and Lapina, M.I., 1997, Inclusions of native Iz are natural diamonds. Our conclusion is sup- metals and other minerals in diamond from kimberlite pipe 50, Liaoning, China: Geochemistry International, Both natural and HPHT synthetic diamonds ported by the following observations. v. 35, p. 695–703. Griffin, W.L., Gain, S.E.M., Adams, D.T., Huang, J-X, Saunders, can contain nitrogen defects. However, the pres- IR-active water, solid CO2, and carbonate ence of fluid inclusions in microdiamonds is and silicate fluid inclusions are exclusive to nat- M., Toledo, V., Pearson, N.J., and O’Reilly, S.Y., 2016, First terrestrial occurrence of tistarite (Ti2O3): Ultra-low oxy- critical to our identification process. Although ural diamonds. They have never been reported gen fugacity in the upper mantle beneath Mount Carmel, hydrocarbons can be contained in HPHT syn- in HPHT synthetic diamonds. Israel: Geology, doi:​10​.1130​/G37910​.1. Hainschwang, T., and Notari, F., 2004, A natural diamond thetic diamonds, IR-active water, solid CO2, and Chromite, moissanite, hematite, magnetite, with very high nickel content: Gems & Gemology, v. 40, carbonate and silicate fluid inclusions have never and magnesiochromite are natural diamond p. 334–336. been reported in HPHT synthetic diamonds. The inclusions. They cannot be formed in HPHT Hainschwang, T., Notari, F., Fritsch, E., and Massi, L., 2006, Natural, untreated diamonds showing the A, B and C in- HPHT synthetic grits in this study do not show synthetic diamonds. frared absorptions (“ABC diamonds”), and the H2 absorp- fluid inclusion–related peaks in their IR spectra. Feldspar, which is the youngest among the tion: Diamond and Related Materials, v. 15, p. 1555–1564, doi:​10​.1016​/j​.diamond​.2005​.12​.029. Therefore, these fluid inclusions strongly sug- observed microinclusions, predates the inven- Hainschwang, T., Fritsch, E., Notari, F., Rondeau, B., and Ka- gest that the microdiamonds are natural in origin. tion of HPHT synthetic diamond grits used for trusha, A., 2013, The origin of color in natural C center Defects in PL spectra, such as NV, nickel, drill bits in the mining industry. bearing diamonds: Diamond and Related Materials, v. 39, p. 27–40, doi:​10​.1016​/j​.diamond​.2013​.07​.007. H2, and 657 nm do not provide a conclusive evi- The inclusions and defects observed in the Hayman, P.C., Kopylova, M.G., and Kaminsky, F.V., 2005, dence for identification. However, we observed microdiamonds suggest that they originated Lower mantle diamonds from Rio Soriso (Juina area, clear differences between the microdiamonds from an unusual geological environment com- Mato Grosso, Brazil): Contributions to Mineralogy and Petrology, v. 149, p. 430–445, doi:​10​.1007​/s00410​-005​ and HPHT synthetic diamonds. Peaks at 565, pared to that of gem-quality diamonds. This -0657​-8. 865, 871, and triplet at 693 nm are exclusive makes them unique, although they are very Howell, D., et al., 2015, Diamonds in ophiolites: Contamina- to the HPHT synthetic diamonds. Two peaks at small. They are not commercially important, but tion or a new diamond growth environment?: Earth and Planetary Science Letters, v. 430, p. 284–295, doi:10​ .1016​ ​ 909 and 953 nm can be detected in the micro- they are geologically important. This research /j​.epsl​.2015​.08​.023. diamonds from chromitite sources, but are not will help to provide a greater understanding of Jacob, D.E., Wirth, R., Enzmann, F., Schwarz, J.O., and Kronz, A., 2009, Microinclusions in polycrystalline diamonds: observed in HPHT synthetic diamonds. diamond genesis. insights into processes of diamond formation: Geophysi- The detection of chromite, magnetite, hema- cal Research Abstracts, v. 11, p. 6791. tite, magnesiochromite, and moissanite provides ACKNOWLEDGMENTS Jaques, A.L., Hall, A.E., Sheraton, J.W., Smith, C.B., Sun, S.S., Drew, R.M., Foudoulis, C., and Ellingsen, K., 1989, Com- We thank Yildirim Dilek and an anonymous reviewer for additional evidence for a natural origin, because position of crystalline inclusions and C-isotope compo- their constructive comments, and Kurt Stuewe for editorial sition of Argyle and Ellendale diamonds, Ross, J., et they have never been observed in the HPHT syn- handling. in thetic diamonds. Microinclusions and macroin- al., eds., Kimberlites and related rocks, 2: Cambridge, Blackwell Scientific, p. 966–989. clusions of these minerals have been reported in REFERENCES CITED Kagi, H., Lu, R., Davidson, P., Goncharov, A.F., Mao, H.K., and natural diamonds around the world. In contrast, Adams, D.M., and Payne, S.J., 1974, Laser-stimulated fluo- Hemley, R.J., 2000, Evidence for ice VI as an inclusion in HPHT synthetics usually contain metallic flux rescence of diamond: Journal of the Chemical Society, cuboid diamonds from high P-T near infrared spectros- Faraday Transactions 2, v. 70, p. 1959–1966, doi:10​ ​.1039​ copy: Mineralogical Magazine, v. 64, p. 1089–1097, doi:​ inclusions, as seen in the synthetic samples used /f29747001959. 10​.1180​/002646100549904. in this study. BenDavid, O.K., Izraeli, E.S., Hauri, E., and Navon, O., 2007, Kopylova, M.G., 2010, The origin of hydrocarbons in fluid in- Fluid inclusions in diamonds from the Diavik mine, Can- clusions in diamonds [abs.], in Proceedings, GeoCanada The observation of the feldspar inclusions ada and the evolution of diamond-forming fluids: Geo- 2010—Working with the Earth: Calgary, Alberta, Canadian seems unimportant because they are not typically chimica et Cosmochimica Acta, v. 71, p. 723–744, doi:10​ ​ Society of Petroleum Geologists, 4 p. found in diamond. However, it is very useful in .1016​/j​.gca​.2006​.10​.008. Lawson, S.C., Fisher, D., Hunt, D.C., and Newton, M.E., 1998, Bulanova, G.P., 1995, The formation of diamond: Journal of On the existence of positively charged single-substitu- this study because of their age. Although we did Geochemical Exploration, v. 53, p. 1–23, doi:10​ .1016​ /0375​ ​ tional nitrogen in diamond: Journal of Physics: Con- not perform an isotope study, it is reasonable to -6742​(94)00016​-5. densed Matter, v. 10, p. 6171–6180, doi:​10​.1088​/0953​ conclude that it took at least a few hundred years Chrenko, R.M., McDonald, R., and Darrow, K., 1967, Infra-red -8984​/10​/27​/016. spectrum of diamond coat: Nature, v. 213, p. 474–476, Leung, I.S., 1990, Silicon carbide cluster entrapped in a dia- for the feldspar to become completely enclosed doi:​10​.1038​/213474a0. mond from Fuxian, China: American Mineralogist, v. 75, inside the diamond by the healing of a fracture. Collins, A.T., 2000, Spectroscopy of defects and transition p. 1110–1119. metals in diamond: Diamond and Related Materials, v. 9, Mainkar, D., Lehmann, B., and Haggerty, S.E., 2004, The cra- Unlike feldspar, other micro­inclusions identified p. 417–423, doi:​10​.1016​/S0925​-9635​(99)00314​-3. ter-facies kimberlite system of Tokapal, Bastar District, in this study are stable in the diamond stability Dasgupta, R., 2013, Ingassing, storage and outgassing of ter- Chhattisgarh, India: Lithos, v. 76, p. 201–217, doi:​10​.1016​ field. Therefore, they formed prior to the feldspar, restrial carbon through geologic time: Reviews in Miner- /j​.lithos​.2004​.04​.024. alogy and Geochemistry, v. 75, p. 183–229, doi:10​ ​.2138​ McKenna, N.M., Gurney, J.J., Klump, J., and Davidson, J.M., and are older than the feldspar inclusions. /rmg​.2013​.75​.7. 2004, Aspects of diamond mineralisation and distribution The patent for diamond tools for machining De Corte, K.D., Cartigny, P., Shatsky, V.S., Sobolev, N.V., and at the Helam Mine, South Africa: Lithos, v. 77, p. 193–208, (i.e., HPHT synthetic, polycrystalline diamonds Javoy, M., 1998, Evidence of fluid inclusions in metamor- doi:​10​.1016​/j​.lithos​.2004​.04​.004. phic microdiamonds from the Kokchetav massif, north- Meyer, H.O.A., 1985, Genesis of diamond: A mantle saga: bonded on carbide substrate) was filed in 1971 ern Kazakhstan: Geochimica et Cosmochimica Acta, v. 62, American Mineralogist, v. 70, p. 344–355. (Wentorf and Rocco, 1973; assignee General p. 3765–3773, doi:​10​.1016​/S0016​-7037​(98)00266​-X. Mita, Y., Nisida, Y., Suito, K., Onodera, A., and Yazu, S., 1990, De Stefano, A., Kopylova, M.G., Cartigny, P., and Afanasiev, Photochromism of H2 and H3 centres in synthetic type Electric Corporation); therefore, HPHT syn- V., 2009, Diamonds and eclogites of the Jericho kim- Ib diamonds: Journal of Physics: Condensed Matter, v. 2, thetic diamond grits were invented fewer than berlite (northern Canada): Contributions to Mineralogy p. 8567–8574, doi:​10​.1088​/0953​-8984​/2​/43​/002.

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Moore, R.O., and Gumey, J.J., 1989, Mineral inclusions in Szabó, C., and Bodnar, R.J., 1995, Chemistry and origin of Xiong, F.H., Yang, J.S., Robinson, P.T., Xu, X.Z., Liu, Z., and Li, Y., diamond from the Monastery kimberlite, South Africa, mantle sulfides in spinel peridotite xenoliths from alka- 2015, Origin of podiform chromitite, a new model based in Ross, J., et al., eds., Kimberlites and related rocks, 2: line basaltic lavas, Nograd-Gomor volcanic field, north- on the Luobusa ophiolite, Tibet: Gondwana Research, Cambridge, Blackwell Scientific, p. 1029–1041. ern Hungary and southern Slovakia: Geochimica et Cos- v. 27, p. 525–542, doi:​10​.1016​/j​.gr​.2014​.04​.008. Novgorodov, P.G., Bulanova, G.P., Pavlova, L.A., Mikhailov, mochimica Acta, v. 59, p. 3917–3927, doi:​10​.1016​/0016​ Xu, X.Z., Yang, J.S., Robinson, P.T., Xiong, F.H., Ba, D.Z., and V.N., Ugarov, V.V., Shebanin, A.P., and Argunov, K.P., 1990, -7037​(95)00265​-2. Guo, G.L., 2015, Origin of ultrahigh pressure and highly Inclusions of potassic phases, coesite and omphacite in Tappert, R., Stachel, T., Harris, J.W., Muehlenbachs, K., and reduced minerals in podiform chromitites and associ- the coated diamond crystal from the “Mir” pipe: Doklady Brey, G.P., 2006, Placer diamonds from Brazil: Indicators ated mantle peridotites of the Luobusa ophiolite, Tibet: Akademii Nauk SSSR, v. 310, p. 439–443. of the composition of the Earth’s mantle and the distance Gondwana Research, v. 27, p. 686–700, doi:​10​.1016​/j​.gr​ Otter, M.L., and Gurney, J.J., 1989, Mineral inclusions in dia- to their kimberlite sources: Economic Geology and the .2014​.05​.010. monds from the Sloan diatremes, Colorado-Wyoming Bulletin of the Society of Economic Geologists, v. 101, Yang, J.S., Robinson, P.T., and Dilek, Y., 2014, Diamonds State Line kimberlite district, North America, in Ross, J., p. 453–470, doi:​10​.2113​/gsecongeo​.101​.2​.453. in ophiolites: Elements, v. 10, p. 127–130, doi:​10​.2113​ et al., eds., Kimberlites and related rocks, 2: Cambridge, Titkov, S.V., Zudin, N.G., Gorshkov, A.I., Sivtsov, A.V., and /gselements​.10​.2​.127. Blackwell Scientific, p. 1042–1053. Magazina, L.O., 2003, An investigation into the cause of Yang, J.S., Meng, F., Xu, X., Robinson, P.T., Dilek, Y., Makeyev, Pavlenko, A.S., Gevorkin, R.G., Aslanyan, A.T., Gulyan, E.K., color in natural black diamonds from Siberia: Gems & A.B., Wirth, R., Wiedenback, M., Griffin, W.L., and Cliff, and Yegorov, O.S., 1974, On the diamonds in the ultra- Gemology, v. 39, p. 200–209, doi:10​ .5741​ /GEMS​ .39​ .3​ .200.​ J., 2015, Diamonds, native elements and metal alloys from chromitites of the Ray-Iz ophiolite of the Polar Urals: mafic belts of Armenia: Geokhimiya, v. 3, p. 366–379. Titus, E., Misra, D.S., Sikder, A.K., Tyagi, P.K., Singh, M.K., Gondwana Research, v. 27, p. 459–485, doi:​10​.1016​/j​.gr​ Robinson, P.T., Trumbull, R.B., Schmitt, A., Yang, J.S., Li, J.W., Misra, A., Ali, N., Cabral, G., Neto, V.F., and Gracio, J., .2014​.07​.004. Zhou, M.F., Erzinger, J., Dare, S., and Xiong, F.H., 2015, 2005, Quantitative analysis of hydrogen in chemical Yelisseyev, A.P., Pokhilenko, N.P., Steeds, J.W., Zedgenizov, The origin and significance of crustal minerals in ophi- vapor deposited diamond films: Diamond and Related D.A., and Afanasiev, V.P., 2004, Features of coated dia- olitic chromitites and peridotites: Gondwana Research, Materials, v. 14, p. 476–481, doi:​10​.1016​/j​.diamond​.2004​ monds from the Snap Lake/King Lake kimberlite dyke, v. 27, p. 486–506, doi:​10​.1016​/j​.gr​.2014​.06​.003. .12​.001. Slave craton, Canada, as revealed by optical topography: Schrauder, M., and Navon, O., 1993, Solid carbon dioxide in Tomilenko, A.A., 2008, Melt and fluid inclusions in diamonds Lithos, v. 77, p. 83–97, doi:​10​.1016​/j​.lithos​.2004​.04​.028. a natural diamond: Nature, v. 365, p. 42–44, doi:10.1038​ ​ and minerals of mantle xenoliths as a source of informa- Zaitsev, A.M., 2001, Optical properties of diamond: A data /365042a0. tion on mantle fluids: International Kimberlite Confer- handbook: Berlin, Springer-Verlag, 502 p. Shigley, J.E., McLure, S.F., Breeding, C.M., Shen, A.H., and ence, 9th, extended abs. 9IKC-A-00375, p. 1–3. Zedgenizov, D.A., Kagi, H., Shatsky, V.S., and Sobolev, N.V., Muhlmeister, S.M., 2004, Lab-grown colored diamonds Tomilenko, A.A., Chepurov, A.I., Pal’yanov, Y.N., Shebanin, 2004, Carbonatitic melts in cuboid diamonds from from Chatham Created Gems: Gems & Gemology, v. 40, A.P., and Sobolev, N.V., 1998, Hydrocarbon inclusions in Udachnaya kimberlite pipe (Yakutia): Evidence from vi- p. 128–145, doi:​10​.5741​/GEMS​.40​.2​.128. synthetic diamonds: European Journal of Mineralogy, brational spectroscopy: Mineralogical Magazine, v. 68, Sobolev, N.V., Yefimova, E.S., Channer, D.M.D., Anderson, v. 10, p. 1135–1142, doi:​10​.1127​/ejm​/10​/6​/1135. p. 61–73, doi:​10​.1180​/0026461046810171. P.F.N., and Barron, K.M., 1998, Unusual upper mantle Welbourn, C.M., Rooney, M.-L.T., and Evans, D.J.F., 1989, Zedgenizov, D.A., Shiryaev, A.A., Shatsky, V.S., and Kagi, H., beneath Guaniamo, Guyana Shield, Venezuela: Evi- A study of diamonds of cube and cube-related shape 2006, Water-related IR characteristics in natural fibrous dence from diamond inclusions: Geology, v. 26, p. 971– from the Jwaneng mine: Journal of Crystal Growth, v. 94, diamond: Mineralogical Magazine, v. 70, p. 219–229, doi:​ 974, doi:10​ .1130​ /0091​ -7613​ (1998)026​ <0971:​ UUMBGG>2​ ​ p. 229–252, doi:​10​.1016​/0022​-0248​(89)90622​-2. 10​.1180​/0026461067020325. .3.CO;2.​ Wentorf, R.H., Jr., and Rocco, W.A., 1973, Diamond tools for Sobolev, N.V., Logvinova, A.M., Zedgenizov, D.A., Seryotkin, machining: United States Patent Grant US3745623 A, Y.V., Yefimova, E.S., Floss, C., and Taylor, L.A., 2004, Min- https://www.google.com/patents/US3745623. eral inclusions in microdiamonds and macrodiamonds Woods, G.S., 1986, Platelets and the infrared absorption of MANUSCRIPT RECEIVED 29 JULY 2016 from kimberlites of Yakutia: A comparative study: Lithos, type Ia diamonds: Royal Society of London Proceedings, REVISED MANUSCRIPT RECEIVED 16 NOVEMBER 2016 v. 77, p. 225–242, doi:​10​.1016​/j​.lithos​.2004​.04​.001. ser. A, v. 407, p. 219–238, doi:​10​.1098​/rspa​.1986​.0094. MANUSCRIPT ACCEPTED 7 FEBRUARY 2017

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