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Allan Hills A81013
Basic information Name: Allan Hills A81013
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA81013
This meteorite may also be called Allan Hills 81013 (ALH 81013) in publications.

Observed fall: No
Year found: 1981
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 17.73 kg
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 6(1)  (1983)  Iron
AMN 13(1)  (1990)  IIA
Meteoritical Bulletin:  MB 76  (1994)  IIA
NHM Catalogue:  5th Edition  (2000)  IIAB
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 6(1):

Sample No.: ALHA81013

Location: Allan Hills

Field No.: 1645

Weight (gms): 17727.0

Meteorite Type: Hexahedrite

Physical Description: Roy S. Clarke, Jr.

The highly distinctive external appearance of this specimen suggests that it is a fragment that separated during atmospheric break up from a larger mass with cubic cleavage. Its shape is that of a cube that has been shortened along one axis by severe and irregular ablation-sculpturing of a face. This face is the only one that is deeply sculptured with thumb-size regmaglypts, giving the impression that it was part of the exterior surface prior to fragmentation. Its opposite face is approximately square, with slightly rounded edges, and appears to have been the leading surface during late stage ablation. All of the surfaces are covered with a thin reddish-brown coating of secondary oxides which are somewhat thicker within the deeper depressions of regmaglypts. Thin cracks several centimeters long are present on all surfaces and tend to parallel the cubic axes of the specimen. Dimensions: 16 x 16 x 11 cm.

 

Tentative Classification: Roy S. Clarke, Jr.

A median slice was removed perpendicular to the square section of the specimen and parallel to opposite sides. One side of the slice was2pol-ished and macroetched, resulting in an area of approximately 140 cm2 available for examination at low magnification. The matrix appears to be single crystal kamacite that etches to a dull finish, atypical for hexahedrites. Several small troilite-daubreelite inclusions are present, as are a few small schreibersites. Slight variations in kamacite reflectivity appear to be due to tiny schreibersites that are unresolvable at low magnification. The most prominent surface feature is the system of orthogonal cracks mentioned above. They penetrate into the interior of the specimen. Neumann bands are absent. This cursory examination suggests that the meteorite is a hexahedrite of somewhat unusual metallography. It probably represents a separate fall, distinct from the typical hexahedrite ALHA78100.

Data from:
  MB76
  Table 2
  Line 536:
Origin or pseudonym:Near Western
Mass (g):17727
Class:IIA
Comments:78100 pairing group
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 6(1) (1983), 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° 44' 51"S, 158° 50' 36"E)
Note: the NHM and MetBase coordinates are 21.4 km apart

Statistics:
     This is 1 of 33930 approved meteorites from Antarctica (plus 6798 unapproved names)
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