Carbonado

Recognized 1840’s
Bahia Province, Brazil Terrestrial History

The name carbonado, meaning burnt or carbonized in Portuguese, was given to this material upon its discovery in Brazil in the 1840’s. This dark gray to black variant of diamondOne of the naturally occurring forms of carbon found in meteorites. Each C atom is bonded through covalent sp3 hydrid orbitals to four others. The strength of the C-C bonds makes diamond the hardest naturally occurring substance (according to the Mohs scale) in terms of resistance to scratching. There are has been mined in the Bahia Province of Brazil since that time. Due to its much greater hardness than typical diamond, it is used industrially for drills and for edges in cutting implements. Carbonado was subsequently found to occur in the same sedimentary geological horizon on a separate continent—in the Ubangui region of the Central African Republic, and has also been reported to occur in Venezuela and the Soviet Union. Carbonado diamond is unique to these limited regions, and it has never been found during any conventional diamond mining and processing operations around the world. The largest recorded carbonado, weighing 3,167 carats (633.4 grams) and named ‘Sergio’, was found in Brazil in 1905.

In the ongoing debate to explain the circumstances surrounding the terrestrial occurrence of this unusual diamond, the theory which posits an arrival during a Precambrian (late Archaean) impact event has remained one of the primary contenders. The arrival occurred at a time when the present-day continents of South America and Africa formed a unified supercontinent known as Rodinia. A magnetic anomaly discovered in Central Africa, encompassing an area over 700,000 km², has also been dated to the Precambrian time. This impact feature, the largest known on Earth, might be associated with the delivery of the carbonado diamonds.

In a contrary opinion, S. Master (1998) proposed that the Precambrian feature known as the Kogo Structure in Equatorial Guinea (1° 11′ N., 10° 1′ E.), measuring 4.67 km in diameter, would have been situated exactly between the Brazilian and Central African carbonado source locations at the time of its occurrence. He determined that a direct relationship exists between the size of the carbonados and their distance from the Kogo Structure, and suggested that this is the probable impact point from which these diamonds were disseminated. The diagram below presented by Stephen E. Haggerty (2014) shows the only known site of carbonado as it appeared ~1.1 b.y. ago, on the Congo–São Francisco craton (age 3.3–3.7 b.y.; Barbosa and Sabate, 2004). This craton was either part of the Rodinia supercontinent or the pre-Rodinia supercontinent Nuna, the latter of which likely existed between ~1.78 b.y. and ~1.40 b.y. ago (Zhang et al., 2012). The Congo–São Francisco craton, at the time part of Gondwonaland, broke up ~180 m.y. ago into what is now Brazil and the Central African Republic.
Image credit: Stephen E. Haggerty, Earth-Science Reviews, vol. 130, pp. 49–72 (March 2014, open access link)
‘Carbonado: Physical and chemical properties, a critical evaluation of proposed origins, and a revised genetic model’
(https://doi.org/10.1016/j.earscirev.2013.12.008) Physical Characteristics

As described by Garai et al. (2006), carbonados are porous (5–15 vol%; Haggerty, 2017), polycrystalline aggregates of sub-µm- to µm-sized, mostly cuboid-shaped diamond crystallites in random orientation. The nodules have a polished surface rind reminiscent of a fusion crustMelted exterior of a meteorite that forms when it passes through Earth’s atmosphere. Friction with the air will raise a meteorite’s surface temperature upwards of  4800 K (8180 °F) and will melt (ablate) the surface minerals and flow backwards over the surface as shown in the Lafayette meteorite photograph below., and it is considered likely that entry- and impact-related processes, including partial ablationGradual removal of the successive surface layers of a material through various processes. • The gradual removal and loss of meteoritic material by heating and vaporization as the meteoroid experiences frictional melting during its passage through the atmosphere. The resulting plasma ablates the meteor and, in cases where a meteor at extremely high temperatures in Earth’s primordial oxygen-poor atmosphere, melted an initially porous texture. Thereafter, secondary mineralization filled the remaining surface pores with silica-based minerals. The interior of carbonado nodules is highly vesiculated, with some pores measuring up to 1 mm in size, and polycyclic aromatic hydrocarbons (PAHs) fill the pores (Kletetschka et al., 2000).

In their magnetization studies of carbonado, Kletetschka et al. (2000) found that magnetic carriers are only present at the smooth surface of carbonado nodules and that the nodules are completely non-magnetic throughout the interior. This suggests that the magnetic carriers were not present at the initial site of carbonado formation, but instead were added during the ablation process in Earth’s atmosphere and/or during secondary terrestrial weathering processes. This finding is contrary to what one would findMeteorite not seen to fall, but recovered at some later date. For example, many finds from Antarctica fell 10,000 to 700,000 years ago. given an origin within Earth’s crustOutermost layer of a differentiated planet, asteroid or moon, usually consisting of silicate rock and extending no more than 10s of km from the surface. The term is also applied to icy bodies, in which case it is composed of ices, frozen gases, and accumulated meteoritic material. On Earth, the or mantleMain silicate-rich zone within a planet between the crust and metallic core. The mantle accounts for 82% of Earth's volume and is composed of silicate minerals rich in Mg. The temperature of the mantle can be as high as 3,700 °C. Heat generated in the core causes convection currents in.

While the C- and N-isotopic compositions and N abundances of carbonados recovered from Central Africa and Brazil are indistinguishable from each other, they are unlike any known terrestrial-sourced diamond varieties and are inconsistent with either a crustal or mantle origin (Shelkov et al., 1995; A. Pradenas, 2015). These unusual values, such as the isotopically light C content (δ¹³C ~ –27‰ compared to typical upper mantle values of δ¹³C ~ –5‰) and the low N abundances, are consistent with an extraterrestrial origin exemplified by Solar SystemThe Sun and set of objects orbiting around it including planets and their moons and rings, asteroids, comets, and meteoroids. material having high contents of organicPertaining to C-containing compounds. Organic compounds can be formed by both biological and non-biological (abiotic) processes. matter (e.g., carbonaceous chondritesChondrites are the most common meteorites accounting for ~84% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicate minerals (found in both chondrules and fine grained matrix), reduced Fe/Ni metal (found in various states like large blebs, small grains and/or even chondrule rims), and various refractory inclusions (such, comets).
Image credit: Stephen E. Haggerty, Earth-Science Reviews, vol. 130, pp. 49–72 (March 2014, open access link)
‘Carbonado: Physical and chemical properties, a critical evaluation of proposed origins, and a revised genetic model’
(https://doi.org/10.1016/j.earscirev.2013.12.008) Notably, P. Cartigny (2010) has described diamonds from Dachine komatiite (French Guyana) that exhibit high isotopic variability including some with isotopic similarities to carbonado. Therefore, and he suggests a possible formation for carbonado in the high-temperature transition zone at depths >300 km, as compared to depths of 150–300 km for typical diamonds. However, these findings of P. Cartigny (2010) are contrary to other studies which have found different isotopic values as well as a lack of isotopic variability in the transition zone (A. Pradenas, 2015). Moreover, his conclusion is at odds with the fact that carbonado has never been found associated with komatiites.

Spectroscopic analyses of mineralInorganic substance that is (1) naturally occurring (but does not have a biologic or man-made origin) and formed by physical (not biological) forces with a (2) defined chemical composition of limited variation, has a (3) distinctive set of of physical properties including being a solid, and has a (4) homogeneous inclusions in carbonado diamond matrices from Brazilian and Central African source locations reveal the presence of highly reducedOxidation and reduction together are called redox (reduction and oxidation) and generally characterized by the transfer of electrons between chemical species, like molecules, atoms or ions, where one species undergoes oxidation, a loss of electrons,  while another species undergoes reduction, a gain of electrons. This transfer of electrons between reactants metals and metalElement that readily forms cations and has metallic bonds; sometimes said to be similar to a cation in a cloud of electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. A diagonal line drawn alloys, including Fe, Si, Ti, Ni, Ag, FeNi-metal, FeCr-metal, and NiCr-metal, as well as the carbide SiC (De et al., 1998; Garai et al., 2006 and references therein); such highly reducingOxidation and reduction together are called redox (reduction and oxidation) and generally characterized by the transfer of electrons between chemical species, like molecules, atoms or ions, where one species undergoes oxidation, a loss of electrons,  while another species undergoes reduction, a gain of electrons. This transfer of electrons between reactants conditions occur within the deep mantle and are associated with certain solar systemDefinable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with objects (S. Haggerty et al., 2014 and references therein). The presence of these exotic metals and alloys provides further evidence for an extraterrestrial origin for carbonado. The mineral osbornite (TiN) has also been identified in carbonado, a nitride previously found only in certain meteorites and recently acquired through NASA’s Stardust missionSpace mission to study Comet Wild 2 (see http://stardust.jpl.nasa.gov/home/index.html). During the encounter, Stardust performed a variety of tasks including making counts of particles encountered by the spacecraft and real-time analyses of the compositions of these particles and volatiles. It also captured cometary particles using Aerogel and stored them for return to cometConglomeration of frozen water and gases (methane, ammonia, CO2) and silicates that that formed in the outer solar system and orbits the Sun. In recent years, the description of comets has shifted from dirty snowballs to snowy dirtballs with more dust than ice. However, the ratio is less than 10-to-1. Wild 2 (Jones et al., 2003). Theories of Origin

Over the years, various non-impact theories have been put forth to explain the formation of these enigmatic diamonds, including chemical vapor depositionMethod for growing solids in which a gaseous precursor (containing fragments of the desired solid) is decomposed and deposited onto a desired surface. Chemical Vapor Deposition (CVD) is one of the most powerful synthetic methods in material science due to its remarkable flexibility. A variety of surfaces can be coated, (CVD), irradiation of carbonaceous material (e.g., kerogen, coal) over geologic timescales by highly energetic particles emitted from radiogenic U and Th, subduction of crustal organic matter into the mantle, and impact metamorphism of Archaean rock containing concentrated organic biomassComplete dry weight of organic material found in the biosphere.. In their studies of carbonado, Yokochi et al. (2008) found that the cathodoluminescenceEmission of visible light in response to electron bombardment. spectra and the 40Ar values are inconsistent with an impact-generated formation for this diamond, and also that the relatively low concentration of Ar is inconsistent with a CVD origin of carbonado diamond.

Ozima and Zashu (1991) conducted noble gasElement occurring in the right-most column of the periodic table; also called "inert" gases. In these gases, the outer electron shell is completely filled, making them very unreactive. isotopic studies in order to study the mechanism of diamond formation through irradiation by energetic particles. Their results do support the theory of micro-scale diamond formation through high-energy irradiation. They found that carbonado contains a high abundance of radiogenic ⁴He, nucleogenic ²¹Ne, and parentless ¹³⁶Xe and ⁸⁶Kr. This is consistent with implantation through an external radioactive decayProcess in which an isotope's nucleus changes ('decays') to produce another isotope. The original atom is called the 'parent' and the resulting atom, the 'daughter'. There are three modes of radioactive decay: • Emission of a particle (He nucleus) that decreases the atomic number (Z) by 2 and the atomic process, most likely by U and Th in close contact with carbonado (e.g., Ozima and Zashu, 1991; Ozima and Tatsumoto, 1997). However, the exact nature of the metamorphicRocks that have recrystallized in a solid state due to changes in temperature, pressure, and chemical environment. process (e.g., shock compression) by which micro-scale diamonds could have been aggregated into multi-carat-sized carbonado is only speculative at this time. Kletetschka et al. (2000) contend that a high-pressure crustal or upper mantle origin is inconsistent with the highly porous nature of carbonado as well as the indicated temperature of formation of <400°C. Based on the model of radiation-induced crystallizationPhysical or chemical process or action that results in the formation of regularly-shaped, -sized, and -patterned solid forms known as crystals. for micro-diamonds in carbonado, the crystallization age was constrained by the timescale of radiogenic Pb implantation from decay of U or Th—2.6 b.y. (instantaneous formation of micro-diamonds) to 3.8 b.y. (formation of micro-diamonds continued to the present) (Kaminsky, 1994; Ozima and Tatsumoto, 1997). This age range is in accord with that ascertained through Pb–Pb dating of quartzComposed of SiO2, quartz is one of the silica group minerals most common in Earth's crust, but never found in meteorites as inclusions visible to the naked eye. Quartz in meteorites has been found in very small quantities in eucrites, other calcium-rich achondrites, and in the highly reduced E chondrites1., rutile and clay mineralHydrous aluminium phyllosilicates, with variable amounts of Fe, Mg, Ca, Na, K, and other cations. The structure of clay minerals is similar to that of micas, consisting of alternating octrahetral and tetrahedral sheets. They are common weathering products of feldspar and low temperature hydrothermal alteration products. inclusions and matrixFine grained primary and silicate-rich material in chondrites that surrounds chondrules, refractory inclusions (like CAIs), breccia clasts and other constituents. in Brazilian carbonado by Sano et al. (2002).

Robinson (1998) and Vicenzi and Heaney (2001) studied a formation theory which is based on the subduction of a slab containing organic sediments. They determined that the C and N isotopes and the N abundances have values that do not support such an origin for carbonado. Moreover, it is not understood how such diamonds could eventually end up in placer deposits, or why their sizes should only reach to µm-size. In addition, it is considered that subducted organic carbonElement commonly found in meteorites, it occurs in several structural forms (polymorphs). All polymorphs are shown to the left with * indicating that it been found in meteorites and impact structures: a. diamond*; b. graphite*; c. lonsdalite*; d. buckminsterfullerene* (C60); e. C540; f. C70; g. amorphous carbon; h. carbon nanotube*. would be too shallow for diamond formation, which is stable at ~150 km (A. Pradenas, 2015).

Based on examinations of carbonado by Smith and Dawson (1985), and the discovery of lonsdaleiteHexagonal polymorph of carbon (C) that forms from meteoric graphite during impact. The immense heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice (below). Lonsdaleite was first identified from the Canyon Diablo meteorite at Barringer Crater (also known as Meteor Crater) in in yakutite (a carbonado-like diamond from Yakutia (Soviet Union) which is significantly different from carbonado; F. Kaminsky, 1994), they favor the theory of impact metamorphism of Archaean crustal rock containing organic carbon or graphiteOpaque form of carbon (C) found in some iron and ordinary chondrites and in ureilite meteorites. Each C atom is bonded to three others in a plane composed of fused hexagonal rings, just like those in aromatic hydrocarbons. The two known forms of graphite, α (hexagonal) and β (rhombohedral), have. However, no evidence of high-pressure phases of silicaSilicon dioxide, SiO2. such as coesiteHigh-pressure polymorph of silicon dioxide (SiO2). Has the same chemical composition as cristobalite, stishovite, seifertite and tridymite but possesses a different crystal structure. Coesite forms at intense pressures of above about 2.5 GPa (25 kbar) and temperature above about 700 °C, and was first found naturally on Earth in impact and stishoviteDense, high-pressure phase of quartz; so far identified only in shock-metamorphosed, quartz-bearing rocks from meteorite impact craters. Stishovite was synthesized in 1961 before it was discovered at Meteor Crater, Arizona. Its structure consists of parallel chains of single SiO6 octahedra. The octahedra are on their sides, sharing opposing edges. Image have been identified in association with quartz. In addition, A. Pradenas (2015) recognized that the large sizes of some carbonado nodules are inconsistent with an impact origin, and also that the spectroscopic absorptionTransfer of energy to a medium as a particle or electromagnetic radiation passes through it. Absorption of electromagnetic radiation is the combined result of Compton scattering, σ, and photoelectric absorption, τ. It may be quantified: where, t = thickness, ρ = density, and μ = mass absorption coefficient, which combines Compton and photoelectric effects (μ = σ + τ). band typically associated with impact-generated diamond is not present in carbonado.

An extraterrestrial origin for carbonado is supported by recent experiments utilizing Fourier transform infrared (FTIR) spectroscopyTechnique of splitting electromagnetic radiation (light) into its constituent wavelengths (a spectrum), in much the same way as a prism splits light into a rainbow of colors. Spectra are not smooth but punctuated by 'lines' of absorption or emission caused by interaction with matter. The energy levels of electrons in (Haggerty et al., 2006; Garai et al., 2006; Garai, 2012). By exposing carbonado to intense infrared light, they observed peaks primarily corresponding to C–H stretching of diamond hydride, spectra almost identical to that of presolar diamonds found in some meteorites. They assert that the hydrogenLightest and most common element in the universe (~92% by atoms; ~75% by mass). Hydrogen's isotopes are: • ¹H (99.9885 %)
• ²H (0.0115 %), also called deuterium.
• ³H, also called Tritium, is a radioactive (t½ = 12.32 y) by-product of atmospheric thermonuclear tests in Earth's hydrosphere and atmosphere.
serves as the bonding agent (protonation) that sinters the microdiamonds together to form the carbonado. They determined that carbonado diamond is consistent with an origin in a hydrogen-rich environment similar to that of the solar nebulaThe primitive gas and dust cloud around the Sun from which planetary materials formed.. Moreover, the presence of nitrogenPrincipal constituent of the Earth’s atmosphere (78.08 vol. % at ground level). Nitrogen is the fifth most abundant element in the universe by atom abundance. Nitrogen comprises only 3.5 vol. % of the atmosphere of Venus and 2.7 vol. % of Mars’s atmosphere. Nitrogen has two isotopes: 14N (99.632 %) and 15N mono-hydride substitutionReplacement of one ion or ionic group for another in the same structural site in a mineral yielding a solid solution. Most substitution in minerals is of cations which are smaller and essentially sit in a lattice of oxygen anions. Anionic substitution does occur in halides. Substitutions are classified based for C is more similar to that found in presolar diamonds than to terrestrial diamonds, providing a clear argument for an extraterrestrial origin. This substitution is inconsistent with the conditions under which conventional diamonds are formed, i.e., slow cooling over millions of years at high pressures.

As with the nanodiamonds present in some meteorites, carbonado diamonds may have also been produced in a supernovaStellar explosion that expels much or all of the stellar material with great force, driving a blast wave into the surrounding space, and leaving a supernova remnant. Supernovae are classified based on the presence or absence of features in their optical spectra taken near maximum light. They were first categorized explosion. Over time, they would be accreted into a planetesimal or perhaps an iron coreIn the context of planetary formation, the core is the central region of a large differentiated asteroid, planet or moon and made up of denser materials than the surrounding mantle and crust. For example, the cores of the Earth, the terrestrial planets and differentiated asteroids are rich in metallic iron-nickel., as attested by their presence in the Canyon Diablo iron. On the other hand, perhaps the abundant carbonado that was produced broke up into asteroid-sized masses. The Florida International University and Case Western Reserve University research team has proposed that a carbonado-rich asteroid measuring ~1 km in diameter impacted the Earth billions of years ago when Africa and South America were part of a single supercontinent. They argue that the vesiculation present in carbonado was caused by gases escaping under conditions of low-pressure during formation, conditions which are inconsistent with the very high pressures existing at diamond formation depths of >150 km, but which do exist in space.

Other exotic mechanisms of carbonado formation have been proposed over the years. Scientists from Princeton University have postulated the existence of diamond layers within extrasolar carbon-rich planets. Haggerty (1996), supported by observations of astronomers from the Harvard–Smithsonian Astrophysical Observatory and other studies (e.g., Stroud et al., 2011), presumes that carbon was transformed into diamond by the intense shock waves generated during the explosive collapse of a red giantGiant and highly luminous red star in the later stages of stellar evolution after it has left the main sequence. These red stars have a relatively cool surface whose core has burned most of its hydrogen. Red giants lose parts of their atmospheres and thus provide new elements into interstellar starSelf-luminous object held together by its own self-gravity. Often refers to those objects which generate energy from nuclear reactions occurring at their cores, but may also be applied to stellar remnants such as neutron stars. (supernova), resulting in a white dwarfRemnant of a star with mass <8 Msun. White dwarfs have masses <1.4 Msun (the Chandrasekhar mass) and are supported by electron degeneracy pressure. White dwarfs have radii ~Rearth (<0.02 Rsun) and densities ~105-6 g/cm3. No nuclear fusion or gravitational contraction occurs in white dwarfs, they shine by residual heat. and its accompanying planetary nebula. White dwarf stars constitute ~6% of the stars in the solar neighborhood. Either of these mechanisms of diamond formation may have resulted in the injection of massive diamond asteroids into the protosolar cloud which become gravitationally attracted to Earth.

Closer to home, the ice-giant planets Uranus and Neptune are considered by some planetary scientists to potentially produce diamond from methane (CH₄), which constitutes 10–15% of their dense atmospheres. It was theorized and experimentally verified that dissociation of CH₄ will occur at high pressures (≈100 GPa) and temperatures >4000 K to form H2 and hydrocarbons, and possibly diamond (Richters and Kühne, 2013 and references therein). Extreme temperatures and pressures (0.6–1.1 TPa) are hypothesized to exist at great depth on Uranus and Neptune, possibly forming a liquid C metallic outer core which transitions to a solid diamond-rich layer at intermediate depths (Eggert et al., 2010). It was experimentally verified (e.g., Benedetti et al., 1999; M. Ross, Lawrence Livermore National Laboratory) that the conversion of methane to diamond did occur at the high-temperature (2000–3000 K) and high-pressure (10–50 GPa) conditions that exist on Uranus and Neptune (see Diamonds in the Sky, PBS–NOVA, P. Tyson). Under the ultra-high temperature and pressure conditions that exist in mid-layers on Uranus and Neptune, oceans of liquid diamond with solid chunks of diamond floating atop are thought to be plausible, in a manner similar to the unusual behavior of water and its less-dense form of ice (I. Silvera, 2010).

Notably, the Pb–Pb age of carbonado coincides with the period of Solar System history known as the Late Heavy BombardmentPeriod between ~4.0 to 3.8 Ga ago when the Moon and other objects in the Solar System were pounded heavily by wayward asteroids. The evidence for the Late Heavy Bombardment (LHB) includes the lunar maria basins and similar structures elsewhere, such as the Caloris Basin on Mercury and the great, 4.1–3.8 b.y. ago, during which time it is thought that the gas giant planets Jupiter and Saturn, and the ice giant planets Uranus and Neptune, underwent orbital migrations under the influence of mutual resonances (‘Nice model’). Among the effects of the resulting gravitational instabilities was the perturbation of the smaller planetesimalsHypothetical solid celestial body that accumulated during the last stages of accretion. These bodies, from ~1-100 km in size, formed in the early solar system by accretion of dust (rock) and ice (if present) in the central plane of the solar nebula. Most planetesimals accreted to planets, but many – into eccentric orbits, eventually leading some to intersect with the terrestrial planetsRocky planets: Mercury, Venus, Earth, and Mars. These planets have physical characteristics, chemical composition and internal structure similar to the Earth. The terrestrial planets have 0.4% of the total mass of all the planets in the Solar System. Some large satellites of planets are also similar to the characteristics of. Significant collisions with Uranus and Neptune would be likely to occur at this time, and it has been argued that the large obliquity of Uranus is the result of a severe tangential collision with an Earth-sized proto-planet early in its history (A. Brunini, 1995, 2006). It may be conjectured that this unique cataclysmic event might also be responsible for the delivery of carbonado into an Earth-crossing orbitThe elliptical path of one body around another, typically the path of a small body around a much larger body. However, depending on the mass distribution of the objects, they may rotate around an empty spot in space • The Moon orbits around the Earth. • The Earth orbits around at this time.

While the exact origin of carbonado remains a mystery, the accumulating evidence for an extraterrestrial origin, or even possibly an extrasolar origin, provokes much excitement; however, further research is necessary. The photo above shows a 1.07 carat (0.21 g) Brazilian carbonado nodule measuring 6.1 × 5.5 × 4.3 mm with a shiny, porous surface.

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Information for this page was obtained through many published works, including the following (arranged by date):

• The ice layer in Uranus and Neptune. Diamonds in the sky? M. Ross, Nature, vol. 292, pp. 435–436 (30 July 1981)
• Carbonado: Diamond aggregates from early impacts of crystal rocks? Smith and Dawson, Geology, vol. 13, #5, pp. 342–343 (May 1985)
• Constraints from noble-gas contents on the origin of carbonado diamonds. Ozima et al., Nature, vol. 351, #6326, pp. 472–474 (6 June 1991)
• Radiation-induced diamond (carbonado): A possible mechanism for the origin of diamond in primitive meteorites. Ozima and Zashu, MeteoriticsScience involved in the study of meteorites and related materials. Meteoritics are closely connected to cosmochemistry, mineralogy and geochemistry. A scientist that specializes in meteoritics is called a meteoriticist. vol. 26, 54th MetSoc, p. 382 (1991)
• Carbonado and Yakutite: Properties and possible genesis. F. Kaminsky, Proceedings of the 5th International Kimberlite Conference, vol. 2, pp. 136–143 (1991)
• Do the Ubangui diamonds originate from a giant impact? D. Shelkov et al., Meteoritics vol. 29, 57th MetSoc, p. 532 (1994)
• A possible constraint to Uranus’ great collision. A. Brunini, Planetary and Space Science, vol. 43, #8, pp. 1019–1021 (August 1995)
• Carbonado: More clues to a common impact origin for samples from Brazil and the Central African Republic. Shelkov et al., 26th LPSC, pp. 1281–1282 (1995)
• Radiation-induced diamond crystallization: Origin of carbonados and its implications on meteoriteWork in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and nano-diamonds. Ozima and Tatsumoto, Geochimica et Cosmochimica Acta, vol. 61, #2, pp. 369–376 (January 1997)
• Microstructural observations of polycrystalline diamond: a contribution to the carbonado conundrum. De et al., Earth and Planetary Science Letters, vol. 164, #3–4, pp. 421–433 (30 December 1998)
• The Kogo Structure (Equitorial Guinea) as a possible source craterBowl-like depression ("crater" means "cup" in Latin) on the surface of a planet, moon, or asteroid. Craters range in size from a few centimeters to over 1,000 km across, and are mostly caused by impact or by volcanic activity, though some are due to cryovolcanism. for the origin of carbonado diamonds from Brazil and the Central African Republic. S. Master, Meteoritics & Planetary Science, vol. 33, 61st MetSoc, pp. 98–99 (1998)
• Dissociation of CH₄ at high pressures and temperatures: Diamond formation in giant planetThe term "planet" originally comes from the Greek word for "wanderer" since these objects were seen to move in the sky independently from the background of fixed stars that moved together through the seasons. The IAU last defined the term planet in 2006, however the new definition has remained controversial. interiors? Benedetti et al., Science, vol. 286, #5437, pp. 100–102 (1 Oct 1999)
• Carbon isotopeOne of two or more atoms with the same atomic number (Z), but different mass (A). For example, hydrogen has three isotopes: ¹H, ²H (deuterium), and ³H (tritium). Different isotopes of a given element have different numbers of neutrons in the nucleus. and nitrogen analysis of carbonado by secondary ionAtom with a net electrical charge because it has lost, or gained, one or more electrons relative to the number possessed by a neutral atom of the same element. A positively charged ion (cation) has fewer electrons than a neutral atom; a negatively charged ion (anion) has more. mass spectrometry (SIMS). Subarnarekha et al., Ninth Annual V. M. Goldschmidt Conference (1999)
• Diamonds in the Sky. P. Tyson, NOVAStar that, over a period of a few days, becomes 10^{3 to} 10⁴ times brighter than it was previously. Novae are observed about 10-15 times per year in the Milky Way., PBS Online—WGBH (1 February 2000)
• Magnetic properties of aggregate polycrystalline diamond: implications for carbonado history. G. Kletetschka, Earth and Planetary Science Letters, vol. 181, #3, pp. 279–290 (15 September 2000)
• The carbon and nitrogen isotopic composition of carnonado diamond: An in situ study. Vicenzi and Heaney, 11th Annual V. M. Goldschmidt Conference (2001)
• Ion microprobeAn instrument in which a focused beam of ions ionizes atoms in a sample and ejects them for analysis with a mass spectrometer. Pbï ¿ ½Pb dating of carbonado, polycrystalline diamond. Sano et al., Precambrian Research, vol. 113, #1-2, pp. 155–168 (2002)
• A new nitride mineral in carbonado. Jones et al., Eighth International Kimberlite Conference Abstracts, Victoria, Canada, p. A95 (2003)
• Archean and Paleoproterozoic crust of the São Francisco Craton, Bahia, Brazil: geodynamic features. Barbosa and Sabate, Precambrian Research, Vol. 133, #1-2, pp. 1–27 (2004)
• Extrasolar Planets May Have Diamond Layers. M. Kuchner (Princeton University) and S. Seager (Carnegie Institute of Washington), press release from Princeton University (7 February 2005)
• Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets. Gomes et al., Nature, vol. 435, pp. 466ï ¿ ½469 (26 May 2005)
• Origin of the obliquities of the giant planets in mutual interactions in the early Solar System. A. Brunini, Nature, vol. 440, pp. 1163–1165 (27 April 2006)
• Infrared absorption investigations confirm the extraterrestrial origin of carbonado diamonds. Garai et al., The Astrophysical Journal Letters, vol. 653, #2, pp. 153–156 (20 December 2006)
• Intragrain Variation In δ¹³C and nitrogen concentration associated with textural heterogeneities of carbonado. Yokochi et al., The Canadian Mineralogist, vol. 46, #5, pp. 1283–1296 (2008)
• Diamond: Molten under pressure. I. Silvera, Nature Physics, vol. 6, pp. 9–10 (1 January 2010)
• Mantle-related carbonados? Geochemical insights from diamonds from the Dachine komatiite (French Guiana). P. Cartigny, Earth and Planetary Science Letters, vol. 296, #3–4, pp. 329–339 (1 August 2010)
• Melting temperature of diamond at ultrahigh pressure. Eggert et al., Nature Physics, vol. 6, pp. 40–43, (2010)
• Supernova Shock-wave-induced co-formation of glassy carbon and nanodiamond. Stroud et al., The Astrophysical Journal Letters, vol. 738, #2 pp. 27–32 (10 September 2011)
• Ionized nitrogen mono-hydride bands are identified in the presolar and carbonado diamond spectra. J. Garai, Meteoritics & Planetary Science, vol. 47, #1, pp. 1–7 (2012)
• Pre-Rodinia supercontinent Nuna shaping up: A global synthesis with new paleomagnetic results from North China, Zhang et al., Earth and Planetary Science Letters, vols. 353–354, pp. 145–155, (2012)
• Liquid methane at extreme temperature and pressure: Implications for models of Uranus and Neptune. Richters and Kühne, Jounal of Experimental and Theoretical Physics Letters. vol. 97, #4, pp. 184–187 (April 2013)
• Carbonado: Physical and chemical properties, a critical evaluation of proposed origins, and a revised genetic model. S. Haggerty, Earth-Science Reviews, vol. 130, pp. 49–72 (March 2014)
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