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Allan Hills A77219
Basic information Name: Allan Hills A77219
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77219
This meteorite may also be called Allan Hills 77219 (ALH 77219) in publications.

Observed fall: No
Year found: 1977 or 1978
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 637 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 1(3)  (1978)  Diogenite - possibly unique
AMN 2(1)  (1979)  Diogenite
AMN 3(2)  (1980)  Mesosiderite
Meteoritical Bulletin:  MB 76  (1994)  Mesosiderite
NHM Catalogue:  5th Edition  (2000)  Mesosiderite
NIPR Catalogue:  2000 Edition  (2000)  Mesosiderite
MetBase:  v. 7.1  (2006)  Mesosiderite-B1
Recommended:  Mesosiderite-B1    [explanation]

This is 1 of 4 approved meteorites classified as Mesosiderite-B1.   [show all]
Search for other: Class B mesosiderites, Metal-rich meteorites, and Mesosiderites
Writeuphelp
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.: ALHA77219

Location: Allan Hills

Field No.: 78012502

Weight (gms): 637.1

Meteorite Type: Mesosiderite

k

Physical Description:

This is not a complete specimen. It is rounded to subangular and a dark brown weathering rind covers the entire stone. Many inclusions of various sizes are present on the highly weathered surface; these objects are glassy, dark greenish-black, and range from angular to subrounded. The inclusions are up to 1 cm in diameter. Approximate diameter: 12 x 8 x 7 cm.

 

Petrographic Description: Brian Mason

The polished thin section is dominated by large orthopyroxene clasts (up to 6 mm across in a groundmass consisting largely of crushed and comminuted orthopyroxene (grains up to 0.6 mm across). The groundmass also contains about 20% of nickel-iron (kamacite and taenite) in grains averaging about 0.3 mm, rare grains of plagioclase (An90), troilite, chromite, merrillite, and a silica polymorph (probably tridymite). The groundmass encloses a rounded aggregate (3 mm across) of fine-grained (up to 0.15 mm) olivine, composition Fa26. The composition of the orthopyroxene clasts and groundmass is somewhat variable, Fs24-28, with CaO ranging from 0.5-2.3%; one grain of diopsidic pyroxene was analyzed, Wo43En45Fs12. The major material of this section is characteristic of a diogenite; however, the presence of a considerable amount of nickel-iron and the olivine enclave is unique for this class of achondrites, and suggests a possible affinity to the mesosiderites. The identification as a mesosiderite has been confirmed by examination of a cut surface of the whole specimen.

Data from:
  MB76
  Table 2
  Line 175:
Origin or pseudonym:Near Western
Mass (g):637.1
Class:Meso
Weathering grade:B
Fayalite (mol%):26
Ferrosilite (mol%):24-28
Comments:NTL=8±2; 77219 pairing group
Catalogs:
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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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Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (76° 43'S, 159° 40'E)
     Recommended::   (76° 43'S, 159° 40'E)

Statistics:
     This is 1 of 33933 approved meteorites from Antarctica (plus 6798 unapproved names)
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