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Allan Hills A81025
Basic information Name: Allan Hills A81025
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA81025
This meteorite may also be called Allan Hills 81025 (ALH 81025) in publications.

Observed fall: No
Year found: 1981
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 379 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 6(1)  (1983)  LL3
AMN 7(1)  (1984)  L3
Meteoritical Bulletin:  MB 76  (1994)  L3.6
NHM Catalogue:  5th Edition  (2000)  L3.6
MetBase:  v. 7.1  (2006)  L3.6
Recommended:  L3.6    [explanation]

This is 1 of 57 approved meteorites classified as L3.6.   [show all]
Search for other: L chondrites, L chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Writeuphelp
Writeup from AMN 6(1):

Sample No.: ALHA81025

Location: Allan Hills

Field No.: 1598

Weight (gms): 379.0

Meteorite Type: LL3 Chondrite

 

Physical Description: Roberta Score

Although ALHA81025 is extremely weathered, many clasts, both rounded and irregular, are apparent on the exterior. One notable exterior clast is 7 x 5 mm in diameter. The bottom surface is iridescent brown and covered with squall-like marks. The interior is extensively weathered. Dimensions: 9.5 x 8 x 4.5 cm.

 

Petrographic Description: Brian Mason

The section shows a close-packed aggregate of chondrules and chondrule fragments up to 3.5 mm across; in a fine-grained matrix of olivine, pyroxene, troilite, and a little nickel-iron. Chondrule types include porphyritic olivine, granular olivine and olivine-pyroxene, barred olivine, and radiating pyroxene. Much of the pyroxene is polysynthetically twinned clinobronzite. Intergranular glass is present in the chondrules, usually turbid but sometimes transparent and purple-brown. Weathering is extensive, with small areas of brown limonite throughout the section. Microprobe analyses show that olivine and pyroxene have variable composition. Olivine composition ranges from Fa1 to Fa41, with a mean of Fa18 (per cent mean deviation FeO is 76). Pyroxene composition ranges from Fs3 to Fs40, with a mean of Fs15 (per cent mean deviation FeO is 75). Purple glass in a chondrule has the following mean composition (weight per cent): SiO2 56.8, Al2O3 24.1, FeO 3.7, MgO 2.4, CaO 0.4 K2O 4.1, Na2O 8.8, TiO2 1.2, MnO 0.69. The texture and the variable mineral compositions indicate type 3, and the low metal content suggests LL group, hence the meteorite is tentatively classified LL3. It is possibly paired with ALHA79003 (Scott et al., Meteoritics, 17, 65-75, 1982), 81030, 81031, and 81032.

Data from:
  MB76
  Table 2
  Line 548:
Origin or pseudonym:Main icefield
Mass (g):379
Class:L3.6
Weathering grade:C
Fayalite (mol%):1-41
Ferrosilite (mol%):3-40
Comments:26Al=45±3; 77011 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° 41' 38"S, 159° 22' 23"E)
Note: the NHM and MetBase coordinates are 8 km apart

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