NORTHWEST AFRICA 7514


R5, rumurutiite
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Found 2005
coordinates not recorded

A large 23.62 kg stone covered by a thin, translucent, olive-gray crust, and not considered to be a meteorite, was gifted by a meteorite collector to T. Stout. In June 2012, a portion was sent to Cascadia Meteorite Laboratory in Oregon (A. Ruzicka and M. Hutson) for analysis, and it was determined that the stone was a meteorite after all—the largest R5 chondrite known, designated NWA 7514.

The interior of this fresh R chondrite appears homogeneous and somewhat featureless in hand section, with an overall gray color. In thin section, chondrules are evident but indistinct, embedded in a transparent matrix. Features are consistent with a shock stage in the range of S2–S4, and the meteorite is virtually unweathered, reflecting the weathering index (wi) value of 0 (Rubin and Huber, 2005). In contrast to some R chondrites which have experienced significant aqueous alteration of their sulfide minerals (mainly pyrrhotite and pentlandite) and contain abundant hydrous phases and brown staining (e.g., amphibole, phlogopite, and apatite in LAP 04840 and MIL 11207; Gross et al., 2013, 2017), the sulfides in NWA 7514 are virtually unaltered, reflecting a formation in dry conditions and a lack of terrestrial aqueous alteration (Ruzicka et al., 2013).

An oxygen three-isotope diagram was prepared from values determined at The Open University, United Kingdom (R. Greenwood), and the plot falls within the Rumuruti-chondrite field. The R-chondrite group is considered to be one of the most oxidized groups of meteorites, and NWA 7514 has the highest Δ17O value of any R chondrite measured to date. The specimen of NWA 7514 shown above is a 0.73 g partial slice. The photo below shows the unusual and awesome main mass.

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Photo courtesy of Tim Stout and Rob Wesel—Nakhla Dog Meteorites