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Physical Characteristics

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  As described by Garai et al. (2006), carbonados are porous (~30%), 
polycrystalline aggregates of sub-µm- to µm-sized, mostly cuboid-shaped, 
diamond crystallites. The nodules have a polished surface rind 
reminiscent of a fusion crust. The interior is highly vesiculated, with 
some vesicles measuring up to 1 mm in size. They believe that entry- and 
impact-related processes, including partial ablation 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. 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 they 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. This finding is contrary to 
what one would find given an origin within Earth's crust or mantle.

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 
(Shelkov et al., 1995); however, these unusual values, such as the 
isotopically light C content and the low N abundances, are consistent 
with an extraterrestrial origin.

Spectroscopic analyses of mineral inclusions in carbonado diamond 
matrices from Brazilian and Central African source locations reveal the 
presence of highly reduced metals and metal alloys, including Fe, Si, 
Ti, Ni, Ag, FeNi-metal, FeCr-metal, and NiCr-metal, as well as the 
carbide SiC (De, 1998; Garai et al., 2006 and references therein). This 
provides further evidence for an extraterrestrial origin for carbonado. 
The mineral osbornite (TiN) has also been identified in carbonado, a 
mineral previously found only in certain meteorites and recently 
acquired through NASA's Stardust mission to comet Wild 2 (Haggerty et 
al., 2006).

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Physical Characteristics Serg Io <invliad@invalid.com> - 2017-02-07 14:09 -0600
  Re: Physical Characteristics noTthaTguY <abu.kuanysh05@gmail.com> - 2017-02-07 15:58 -0800

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