... to polycrystalline diamond. The most commonly used names are framesite, stewartite, diamondite, boart, and carbonado ( Table 1 ). The names used to sub-divide the group originate from the lexica of both industry and academia and are based on appearance (e.g., grain size), application, value, and in some cases...

... natural diamond synthetic diamond carbonado volcano ophiolite contamination ✉ Corresponding author. E-mail adress: [email protected] (N.P. Pokhilenko) Note that neither Silaev et al. ( 2015 ) nor Howell et al. ( 2015 ) paid attention to the presence of microinclusions, which were...

... removal followed by diffusion-limited crystallization of pure carbon. The similarity of the after-coal diamonds features with carbonado is a strong piece of evidence in support of the impact hypothesis for the origin of carbonado. Although impact after-coal diamond products are known from nature...

...Charles W. Magee, Jr.; Guilherme Teles; Edward P. Vicenzi; Wayne Taylor; Peter Heaney Abstract Carbonado is a porous polycrystalline diamond rock found in central African and Brazilian placer deposits. It contains unsupported radiogenic isotopes of He, Ne, Kr, Xe, and Pb. Here we show...

...Richard A. Ketcham; Christian Koeberl Abstract Three-dimensional textural observations of inclusion and porosity patterns in a 23-carat carbonado diamond using high-resolution X-ray computed tomography reveal new information bearing on the nature and origin of this enigmatic material. A prominent...

... phase is transformed by a diffusionless mechanism into a cubic structure at pressures of around 6.5 GPa. A diamond-like BCN phase was synthesized in the form of individual crystals or polycrystalline aggregates. The microstructure of these aggregates is comparable to natural and synthetic carbonado-type...

...Felix V. Kaminsky; Richard Wirth; Luiz Morales Abstract Samples of carbonado from Brazil and the Central African Republic were studied with the use of electron backscatter diffraction (EBSD) for quantitative textural analysis (QTA) and transmission electron microscopy (TEM). The grain size...

...Hidemi Ishibashi; Hiroyuki Kagi; Haruko Sakuai; Hiroaki Ohfuji; Hirochika Sumino Abstract Carbonado, a variety of natural polycrystalline diamond whose origin remains unknown, differs notably in the properties from common diamonds of mantle origin. In this study, infrared spectroscopic...

...Violaine Sautter; Jean-Pierre Lorand; Patrick Cordier; Benjamin Rondeau; Hugues Leroux; Cristiano Ferraris; Sylvain Pont Abstract A unique Brazilian sample of a carbonado, displaying unusually large amount of diamond clasts merged within a fine-grained diamond matrix, has been studied by Secondary...

...Vitaly A. Petrovsky; Andrei A. Shiryaev; Vladimir P. Lyutoev; Alexander E. Sukharev; Maximiliano Martins Abstract The morphology and defects in diamond grains comprising Brazilian carbonado have been investigated using X-ray diffraction, photo- and X-ray luminescence, electron paramagnetic...

...Reika Yokochi; Daniel Ohnenstetter; Yuji Sano Abstract We have investigated the textural diversity in four Brazilian samples of carbonado diamond by cathodoluminescence petrography and spectroscopy, coupled with carbon, nitrogen and argon isotope analyses. Three types of textures were observed...

...Hiroyuki Kagi; Satoshi Fukura Abstract Carbonado diamonds from the Central African Republic (CAR) were investigated using spectroscopic observations. Raman spectra for a polished section of carbonado showed the average Raman frequency as 1333.0 cm −1 ; measurements 10 μm below the sample surface...

...Hiroyuki Kagi; Shuichi Sato; Tasuku Akagi; Hisao Kanda Abstract Carbonado diamonds from the Central African Republic were investigated using spectroscopic observations and C-isotopic analysis. Based on photoluminescence (PL) spectra, carbonado samples were classified into two groups: Group-A, which...

... diamonds reveal the hallmarks of primitive Earth, recycled crustal sources, and crystallization processes. Two lesser known and understood varieties of diamond are, first, natural polycrystalline diamond—carbonado and framesite—and, second, microdiamonds discovered over the last 20 years associated...

...Peter J. Heaney; Edward P. Vicenzi; Subarnarekha De Abstract Polycrystalline aggregates of diamond called carbonado and framesite have excited the attention of scientists because their crystallization histories are thought to depart markedly from established modes of diamond genesis. In contrast...

...Subarnarekha De; Peter J. Heaney; Yingwei Fei; Edward P. Vicenzi Abstract Efforts to simulate the extreme toughness of the polycrystalline diamond variety known as carbonado typically entail the sintering of diamond powders in the presence of metal solvent-catalysts. In this study, we have...

...V.A. Nadolinny; V.S. Shatsky; N.V. Sobolev; D.J. Twitchen; O.P. Yuryeva; I.A. Vasilevsky; V.N. Lebedev Abstract Electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopies have been used to study Brazilian and Central African carbonados. We report the first observation of the N...

...J. V. Smith; J. B. Dawson Abstract Carbonados are irregular polycrystalline aggregates of diamond that occur in placers and low-grade metamorphic rocks. They are characterized by fine grain size, light carbon isotope ratio, a wide variety of inclusions of crustal materials (silicates, phosphates...

...Lucien F. Trueb; E. Christiaan De Wys Abstract Carbon originating from Ubangi (Central African Republic) is a dark-colored variety of polycrystalline diamond resembling Brazilian carbonado. It consists of a porous matrix of randomly oriented, mainly anhedral crystallites ranging from 0.5 to 20 μm...

...L. F. Trueb; W. C. Butterman Abstract Brazilian carbonados consist of mostly anhedral, randomly oriented diamond crystallites with a size ranging from a fraction of a micron to over 20 μm. These crystallites are aggregated and interlocked into porous polycrystalline masses with a microstructure...