CBa, bencubbinite click on photo for a magnified view Purchased August 2005 no coordinates recorded A group of sixty-nine small, paired, stone fragments, having a combined weight of 745.5 g, were recovered in the Sahara Desert by a Moroccan hunter. Further searches of the area have yielded no additional fragments. All of these fragments were subsequently purchased by H. Strufe, and a sample was submitted for analysis to the Museum für Naturkunde, Humboldt University, Berlin, (A. Greshake). Northwest Africa 4025 was classified as a rare CBa bencubbinite.
Northwest Africa 4025 exhibits very close similarities to the type specimen Bencubbin, and has a shock stageA petrographic assessment, using features observed in minerals grains, of the degree to which a meteorite has undergone shock metamorphism. The highest stage observed in 25% of the indicator grains is used to determine the stage. Also called "shock level". of S3 and a weathering grade of W2/3. A visual comparison was conducted between NWA 4025 specimens and the previously found Saharan CBa chondriteChondrites 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 NWA 1814; it was clearly demonstrated that they are not paired. Northwest Africa 4025 closely resembles the Bencubbin 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, while NWA 1814 manifests some characteristics of the CBa chondrite Gujba. Moreover, The degree of terrestrial alteration on the outer surface of NWA 4025 is generally higher than that on NWA 1814. An O-isotopic analysis indicates that a close relationship exists between this bencubbinite and the CH 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.
The CB, CH, and CR chondrites constitute the CR clan, comprising groups which likely formed in the same isotopic reservoir under similar conditions in the solar nebulaThe primitive gas and dust cloud around the Sun from which planetary materials formed.. The best current evidence supports an origin for these late-formed metal-rich carbonaceous chondrites in an impact plume generated by a collision between planetary embryos (Krot et al., 2009). Following condensation of the various components, they were aerodynamically sorted according to their velocity, size, and densityMass of an object divided by its volume. Density is a characteristic property of a substance (rock vs. ice, e.g.). Some substances (like gases) are easily compressible and have different densities depending on how much pressure is exerted upon them. The Sun is composed of compressible gases and is much as they spread out into the nebular gas in a typical fan-shaped pattern. It was calculated by Morris et al. (2012) that in ~1% of the impacts the host planetesimal would travel in the direction of the impact plume, sweeping up some of the aerodynamically sorted ejectaFractured and/or molten rocky debris thrown out of a crater during a meteorite impact event, or, alternatively, material, including ash, lapilli, and bombs, erupted from a volcano. within a short time period measured in weeks. They reason that this reaccreted material would have been mixed with existing crustal components to form a layer many meters thick. See the HaH 237 page for a more detailed scenario of the CB group formation process ascertained by Fedkin et al. (2015) through kinetic condensation modeling.
The specimen of NWA 4025 shown above is a 7.6 g prepared end section (half individual). Pictured below are two of the sixty-nine recovered fragments constituting this meteorite.
Photo courtesy of the J. Piatek Collection