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Allan Hills A78100
Basic information Name: Allan Hills A78100
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA78100
This meteorite may also be called Allan Hills 78100 (ALH 78100) in publications.

Observed fall: No
Year found: 1978
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 84.9 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 4(1)  (1981)  IIA
AMN 7(1)  (1984)  IIA
Meteoritical Bulletin:  MB 76  (1994)  IIA
NHM Catalogue:  5th Edition  (2000)  IIAB
NIPR Catalogue:  2000 Edition  (2000)  IIA
MetBase:  v. 7.1  (2006)  IIA
Recommended:  Iron, IIAB    [explanation]

This is 1 of 120 approved meteorites classified as Iron, IIAB.   [show all]
Search for other: IIAB irons, Metal-rich meteorites, and Iron meteorites
Writeuphelp
Writeup from AMN 4(1):

[Addendum to AMN 4(1)]

Sample No.: ALHA78100

Location: Allan Hills

Field No.: 439

Weight (gins): 85.0

Meteorite Type: Hexahedrite (IIA)

 

Physical Description:

This specimen is a thin, flat, slightly irregular plate, 5 cm x 4.5 cm x 0.9 cm. It appears to be an individual that was oriented during atmospheric flight. The anterior surface is rounded at the edges and the posterior surface is flat. Weathering may have been a factor in shaping as the posterior surface is more heavily weathered than the anterior. The posterior surface is covered with an essentially featureless reddish brown oxide. The anterior surface is also oxide covered, but it contains numerous 1 to 2 mm pockmarks. Both surfaces are tool marked from an attempt to cleave the specimen.

 

Tentative Classification: Roy S. Clarke, Jr.

A microetched median section of approximately 3 cm of surface area was examined. It is single crystal kamacite containing Neumann bands and inclusions. Schreibersite is abundant as rhabdites, and is also present as lamellar schreibersite and as hieroglyphic schreibersite surrounding troilite-daubreelite inclusions. Troilite-daubreelite inclusions are also present with only small bordering schreibersites. The anterior surface edge has an ablation rim of α2 averaging about 0.7 mm wide. No α2 was observed on the posterior surface. Fusion crust was not present, and surfaces are covered with terrestrial oxide up to 0.25 mm thick. The specimen appears to be a hexahedrite or Group IIA meteorite.

Data from:
  MB76
  Table 2
  Line 324:
Origin or pseudonym:Main icefield
Mass (g):84.9
Class:IIA
Comments:78100 pairing group
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 4(1) (1981), 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 32969 approved meteorites from Antarctica (plus 6798 unapproved names)
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