Sacramento Wash 005

SULFIDE-IRON from H-chondrite
(H-metal recommended in MetBull 93)
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Found May 18, 2004
34° 44′ 48′ N., 114° 12′ 36′ W. An iron mass weighing 8.6 g was initially found in the Franconia strewn field in in Mojave County, Arizona by Pete Meyers, and several months later (October 29, 2005) a similar type of iron mass also lacking fusion crust and weighing 43.7 g was found by Jim Smaller. Hundreds of individual pieces, most weighing under 1 g, were subsequently recovered in the area. The TKW is recorded as 52.3 g but may be as high as 1,000 g. Samples were analyzed at the University of Arizona (D. Schrader et al.), along with the Kingsborough Community College and the American Museum of Natural History in New York (H. Connolly). A reflected-light photo of a thin section of a Sacramento Wash 005 specimen was described in ‘Meteorite Picture of the Day’ for January 18, 2014 by Laurence Garvie—Center for Meteorite Studies at Arizona State University.

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These iron pieces are reddish-brown in color, indicating mild weathering on the surface, but they show a fresh interior. Most specimens lack fusion crust, although some individuals that were studied exhibited bluish fusion crust with flow lines. Surface pits are thought to have been produced by troilite cell plucking through ablation or later weathering. Sacramento Wash 005 is composed of FeNi-metal (both kamacite and taenite), troilite, metallic copper, chromite, and other minor phases.

Sacramento Wash 005 is very similar to the meteorite MET 00428 and is similar in many respects to HOW 88403 (the latter not derived from the H-chondrite parent body), in that they are all S-rich FeNi-metal meteorites formed in high-temperature environments but experienced varying cooling rates. H-chondrite-like silicates are present in these meteorites, and a chondrule-bearing inclusion (POP and RP type chondrules) comparable to an H4 chondrite was identified in Sacramento Wash 005. It is thought that these Fe- and S-rich meteorites formed by impact-generated melting on the H-chondrite parent body (Schrader et al., 2010). The cellular troilite in Sacramento Wash 005 reflects a relatively slow cooling rate after the impact event, with formation possibly occurring in a subsurface location. More rapid cooling was experienced by meteorites like the impact-melt Sahara 03505.

These iron specimens represent a distinct meteorite type that is different from the H-chondrite-related IIE irons as well as the H-metal meteorite LEW 88432, the latter thought to be a metal nodule extricated from an H-chondrite meteorite host. By contrast, these S-rich irons are thought to have formed by impact-melt processes and are considered to constitute a new subgroup, termed sulfide-iron meteorites, as proposed by D’Orazio et al. (2009); members presently include Sacramento Wash 005, Sahara 03505, RBT 04162/04299, MET 00428, and HOW 88403. The subgram individual fragment of Sacramento Wash 005 shown above was found by J. Smaller and then acquired by J. Humphries during the 2009 Denver Mineral Show. Excellent detailed photos of the interior of SaW 005 iron specimens are shown below courtesy of Mirko Graul.

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Troilite cells in Sacramento Wash 005

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Photos courtesy of Mirko Graul Meteorite

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