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Allan Hills A77271
Basic information Name: Allan Hills A77271
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77271
This meteorite may also be called Allan Hills 77271 (ALH 77271) in publications.

Observed fall: No
Year found: 1977 or 1978
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 610 g
Antarctic Meteorite Newsletter:  AMN 1(3)  (1978)  H6
Meteoritical Bulletin:  MB 76  (1994)  H6
NHM Catalogue:  5th Edition  (2000)  H6
MetBase:  v. 7.1  (2006)  H6
Recommended:  H6    [explanation]

This is 1 of 6438 approved meteorites (plus 5 unapproved names) classified as H6.   [show all]
Search for other: H chondrites, H chondrites (type 4-7), Ordinary chondrites, and Ordinary chondrites (type 4-7)
Writeup from AMN 1(3):
This text was reprinted from AMN 1(3) in AMN 4(1). In some cases, it may be an updated version from the original.

Sample No.: ALHA77271

Location: Allan Hills

Field No.: Y78010603

Weight (gms): 609.5

Meteorite Type: H6 Chondrite


Physical Description:

This is a complete, rounded specimen. Approximately 25% of the total sample is covered with a dull black fusion crust. The crust appears in small patches on the meteorite's surface and is approximately 1 mm thick. The portion of the meteorite not covered with fusion crust is a dark brown weathered surface. Small inclusions are visible on this surface. The sample was difficult to chip. When the material was collected for thin section preparation, no fresh metal was observed. The sample fractured along a small fissure. The interior of the bulk meteorite was weathered along this fissure. Dimensions approximately 8.0x7.5x5.0 cm.


Petrographic Description: Brian Mason

Chondrules are sparse and tend to merge with the granular groundmass, which consists largely of subequal amounts of olivine and orthopyroxene with minor amounts of nickel-iron (~20%), plagioclase (~10%), and troilite (~5%). Microprobe analyses show olivine (Fa19), orthopyroxene (Fs16), and plagioclase (An13) of uniform composition. The section shows a moderate degree of weathering, with small areas and veins of brown limonite.

Data from:
  Table 2
  Line 222:
Origin or pseudonym:Main icefield
Mass (g):609.5
Weathering grade:C
Fayalite (mol%):18
Ferrosilite (mol%):16
Comments:26Al=39±2; 77271 pairing group
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References: Published in Antarctic Meteorite Newsletter 1(3) (1978), JSC, Houston
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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     Catalogue of Meteorites:   (76° 43'S, 159° 40'E)
     Recommended::   (76° 43'S, 159° 40'E)

     This is 1 of 43700 approved meteorites from Antarctica (plus 3802 unapproved names)
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