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Allan Hills A81024
Basic information Name: Allan Hills A81024
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA81024
This meteorite may also be called Allan Hills 81024 (ALH 81024) in publications.

Observed fall: No
Year found: 1981
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 798 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 6(1)  (1983)  L3
Meteoritical Bulletin:  MB 76  (1994)  L3.6
NHM Catalogue:  5th Edition  (2000)  L3.6
MetBase:  v. 7.1  (2006)  H3.6
Antarctic Meteorite Newsletter:  AMN 33(1)  (2010)  H3.6
Recommended:  H3.6    [explanation]

This is 1 of 43 approved meteorites classified as H3.6.   [show all]
Search for other: H chondrites, H chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Writeuphelp
Writeup from AMN 6(1):

Sample No.: ALHA81024

Location: Allan Hills

Field No.: 1510

Weight (gms): 797.7

Meteorite Type: L3 Chondrite

Physical Description: Carol Schwarz

This angular specimen is covered by black blistery fusion crust; some areas are reddish-brown. Several deep fractures penetrate the specimen. The interior exposed in chipping is reddish-brown and appears to be extremely weathered. Dimensions: 10 x 8 x 6.5 cm.

Petrographic Description: Brian Mason

The section shows a close-packed aggregate of chondrules, up to 1.5 mm across; a variety of types is present, including porphyritic olivine, barred olivine, granular olivine and olivine-pyroxene, and fine-grained pyroxene. Much of the pyroxene is polysynthetically twinned clinobronzite. Some intergranular glass within the chondrules is pale brown and transparent, but commonly is turbid and partly devitrified. Minor amounts of nickel-iron (largely altered to brown limonite) and troilite are present in the matrix. Olivine and pyroxene have variable composition. Olivine composition ranges from Fa3 to Fa28, with a mean of Fa19 (% mean deviation FeO is 34). Pyroxene composition ranges from Fs2 to Fs24, with a mean of Fs10 (% mean deviation FeO is 79). Transparent chondrule glass has the following mean composition (weight per cent): SiO2 63.3, Al2O3 22.5, FeO 0.9, MgO 0.2, CaO 0.2, K2O 3.3, Na2O 8.8, TiO2 0.8, MnO 0.03; this composition is close to anorthoclase. The texture and the variable mineral compositions are that of type 3, and the amount of metal suggests L group, hence the meteorite is tentatively classified L3. It is possibly paired with ALHA77011 and many other L3 chondrites from the Allan Hills.

Data from:
  MB76
  Table 2
  Line 547:
Origin or pseudonym:Main icefield
Mass (g):797.7
Class:L3.6
Weathering grade:C
Fayalite (mol%):3-28
Ferrosilite (mol%):2-24
Comments:26Al=40±2
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° 40' 42"S, 159° 15' 58"E)
Note: the NHM and MetBase coordinates are 11.1 km apart

Statistics:
     This is 1 of 39173 approved meteorites from Antarctica (plus 5051 unapproved names)
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