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Yamato 791200
Basic information Name: Yamato 791200
     This is an OFFICIAL meteorite name.
Abbreviation: Y-791200
Observed fall: No
Year found: 1979
Country: Antarctica [Collected by National Institute of Polar Research, Japan]
Mass:help 51.6 g
Classification
  history:
NHM Catalogue:  5th Edition  (2000)  Diogenite
NIPR Catalogue:  2000 Edition  (2000)  Diogenite-B
MetBase:  v. 7.1  (2006)  Diogenite
Recommended:  Diogenite    [explanation]

This is 1 of 481 approved meteorites classified as Diogenite.   [show all]
Search for other: Achondrites, Diogenites, and HED achondrites
Writeuphelp
Writeup from MN J7(1):

Y-791200, 81-1: Diogenite (Type B diogenitic with cumulate eucrites)

          This specimen is texturally similar to the Y-75032-type achondrite and includes small amounts of a cumulate-eucrite component. A coarse-grained noritic clast, which is exposed on the surface of the hand specimen, has inverted pigeonite with blebby inclusions of augite but is not present in the thin section examined. Very dark glassy matrix fills the interstices between subangular fragments of shocked pyroxene. Plagioclase and chromite are not rare as fragments, but are very rare in the lithic clasts. The plagioclase is actually devitrified maskelynite and the largest fragment, probably from a noritic source rock, is 1.2 x 0.65 mm in size. The modal abundance of plagioclase is 9% for this thin section, and 10% for another. This specimen has some of the features of a cumulate eucrite, and may be polymict or more precisely termed genomict.

          One large pyroxenite clast, 1.6 x 1.4 mm in size, consists of a few grains of orthopyroxene with irregularly thickened and thinned lamella-like inclusions of augite on (100). The pyroxene may be low-Ca inverted pigeonite. A very small plagioclase grain is in the rim of this clast. Another gabbroic clast, 1.2 x 1.3 mm in size, consists almost entirely of shocked low-Ca pyroxene Ca3Mg62Fe35, small 'primary' augite grains Ca40Mg44Fe17 (bulk), 0.75 x 0.34 mm in size, with fine exsolution lamellae plagioclase (An82).

          The alumina contents in the shocked glass range from 5-7 wt%. The large size of augite indicates that it is not granule exsolution.

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Search for this meteorite in the NIPR database (Japan):   
References: Published in Meteorites news : Japanese collection of Antarctic meteorites / Meteorites news : Japanese collection of Antarctic meteorites ,7(1),1-94 (1998-06)
Never published in the Meteoritical Bulletin
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Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (71° 30'S, 35° 40'E)
     Recommended::   (71° 30'S, 35° 40'E)

Statistics:
     This is 1 of 41899 approved meteorites from Antarctica (plus 3802 unapproved names)
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