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Yamato 791438
Basic information Name: Yamato 791438
     This is an OFFICIAL meteorite name.
Abbreviation: Y-791438
Observed fall: No
Year found: 1979
Country: Antarctica [Collected by National Institute of Polar Research, Japan]
Mass:help 20.2 g
NHM Catalogue:  5th Edition  (2000)  Eucrite-mmict
NIPR Catalogue:  2000 Edition  (2000)  Eucrite-mmict
MetBase:  v. 7.1  (2006)  Eucrite-mmict
Recommended:  Eucrite-mmict    [explanation]

This is 1 of 272 approved meteorites classified as Eucrite-mmict.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Writeup from MN J7(1):

Y-791438, 51-1: Eucrite (magnesium non-cumulate eucrite)

          Y-791438 is a crystalline, magnesian non-cumulate eucrite. Y-791438 is composed mainly of plagioclase (36 vol.%) and pyroxene. Minor minerals include ilmenite, chromite, troilite, Ca phosphates and zircon. The texture of Y-791438 is slightly disturbed by shock events, but the original texture seems to have been ophitic with the sizes of pyroxene ranging from 0.5 to 1 mm in length and those of plagioclase from 0.2 to 0.8 mm. Pigeonite crystals show fine exsolution lamellae (width 1 to 2 microns) of augite on (001). A large grain of pigeonite may be partly inverted to orthopyroxene in different orientations, but this texture is different from that of cumulate eucrites in that the width of exsolution lamellae of cumulate eucrite is more than 10 microns and orthopyroxene crystals grow in much larger scale. There is another portion in Y-791438, with very different appearance indicating a secondary shock event. About a half of the pyroxene grain-boundaries are covered with fuzzy glassy materials with chemical compositions intermediate between augite and plagioclase. Globules of Fe-S ranging from 0.5 mm to 1 mm microns in diameter often observed in such areas. The bulk composition of the pigeonite is Ca8Mg50Fe42, which is similar to those of cumulate eucrites. Most of the plagioclase crystals shows slight normal zoning. The An contents of plagioclase range from An95 to An90. The range of An is smaller than that in ordinary eucrites, but larger than those of cumulate eucrites.

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

     This is 1 of 43856 approved meteorites from Antarctica (plus 3802 unapproved names)
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