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Allan Hills A77004
Basic information Name: Allan Hills A77004
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77004
This meteorite may also be called Allan Hills 77004 (ALH 77004) in publications.

Observed fall: No
Year found: 1977
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 2.23 kg
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 2(1)  (1979)  H4
Meteoritical Bulletin:  MB 76  (1994)  H4
NHM Catalogue:  5th Edition  (2000)  H4
NIPR Catalogue:  2000 Edition  (2000)  H4
MetBase:  v. 7.1  (2006)  H4
Recommended:  H4    [explanation]

This is 1 of 5779 approved meteorites (plus 2 unapproved names) classified as H4.   [show all]
Search for other: H chondrites, H chondrites (type 4-7), Ordinary chondrites, and Ordinary chondrites (type 4-7)
Writeuphelp
Writeup from AMN 2(1):
This text was reprinted from AMN 2(1) in AMN 4(1). In some cases, it may be an updated version from the original.

Sample No.: ALHA77004

Location: Allan Hills

Field No.: 77122902

Weight (gms): 2230.0

Meteorite Type: H4 Chondrite

 

Physical Description:

The angular specimen, 7.0x5.5x2.0 cm, has many parallel fractures. Only the B surface has dull, brownish-black fusion crust. The other surfaces are weathered orangish-brown. Because of the severity of the weathering, it is impossible to define the shape, size, and color of the inclusions. When attempting to obtain a suitable thin section sample, the stone broke into six documented pieces. All pieces are severely weathered; no non-weathered surfaces were observed.

 

Petrographic Description: Brian Mason

The section shows well-developed chondritic structure, the chondrules ranging from 0.2-0.8 mm in diameter; a variety of types is present, the commonest being barred olivine, porphyritic olivine, and fine-grained or granular pyroxene. Much of the granular pyroxene is polysynthetically-twinned clinobronzite. Some of the chondrules are fragmented. The chondrules are set in a fine-grained granular matrix consisting largely of olivine and pyroxene, with minor amounts of nickel-iron and troilite (nickel-iron in greater amount than troilite). The section is pervaded with brown limonitic staining, and veins and patches of limonite are associated with many of the metal grains. Microprobe analyses show olivine with slightly variable composition (Fa18) and pyroxene with greater variability (Fs15-27, average Fs16).

Data from:
  MB76
  Table 2
  Line 13:
Origin or pseudonym:Near Western
Mass (g):2230
Class:H4
Weathering grade:C
Fayalite (mol%):17-20
Ferrosilite (mol%):15-27
Comments:26Al=52±5; NTL=35.5±0.3; 77004 pairing group
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 2(1) (1979), 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 39173 approved meteorites from Antarctica (plus 5051 unapproved names)
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