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Yamato 791000
Basic information Name: Yamato 791000
     This is an OFFICIAL meteorite name.
Abbreviation: Y-791000
Observed fall: No
Year found: 1979
Country: Antarctica [Collected by National Institute of Polar Research, Japan]
Mass:help 90.4 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 J6(1):

Y-791000, 82-1: Diogenite

         Large fragments of pyroxene, often partly including dark glassy appearance are set in glassy matrix with more comminuted pyroxene fragments. Some pyroxenes include fine lamellae, or blebby augites. Small rounded fragments of plagioclase are rarely found in the glassy matrix. This specimen is texturally very similar to Y-75032. Large coarse-crystalline clasts and comminuted pyroxene fragments are set in a very dark brown  glassy matrix with an aluminous pigeonite composition. The alumina contents range from 4-8 wt%. The amount of glass varies from one place to the other, and the normative plagioclase in the glass is 19%. The pyroxene texture and chemistry are the same as those of Y-75032. Orthopyroxene with high-Ca bulk composition and abundant oriented blebby inclusions of augite may have originally been law-Ca pigeonite, but other grains with fine regular lamellae of augite are probably primary orthopyroxene.

         Plagioclase and chromite grains are present in both the clasts and matrix. Although inverted pigeonite is present, this specimen is on the diogenite side of the continuum between diogenite and cumulate eucrite. The modal abundance of plagioclase is less than 3%. Because there is 3% plagioclase in Rhoda and more in diogenites containing basalt clasts, this specimen may be regarded as a special diogenite. A pyroxene clast, 2.3x2.0 mm in size contains a few grains of pyroxene (bulk composition Ca5Mg64Fe31) with blebby augite inclusions in a few areas and angular interstitial plagioclase with An contents (avg 90) from 87 to 92. This clast is similar to that in Y-75032. Another pyroxene clast, 1.8 mm in diameter, consists of two pyroxene grains with scattered augite blebs and fine regular augite lamellae with (100) in common. The fine augite lamellae nucleated on the blebs. Plagioclase is not found in some pyroxene clasts.

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References: Published in Meteorites news : Japanese collection of Antarctic meteorites /Meteorites news : Japanese collection of Antarctic meteorites ,6(1),1-47 (1996-03)
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 41908 approved meteorites from Antarctica (plus 3802 unapproved names)
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