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Allan Hills A81251
Basic information Name: Allan Hills A81251
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA81251
This meteorite may also be called Allan Hills 81251 (ALH 81251) in publications.

Observed fall: No
Year found: 1981
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 158 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 6(1)  (1983)  LL3
Meteoritical Bulletin:  MB 76  (1994)  LL3.2/3.4
NHM Catalogue:  5th Edition  (2000)  LL3.2/3.4
MetBase:  v. 7.1  (2006)  LL3.3
Antarctic Meteorite Newsletter:  AMN 33(1)  (2010)  LL3.3
Recommended:  LL3.3    [explanation]

This is 1 of 15 approved meteorites classified as LL3.3.   [show all]
Search for other: LL chondrites, LL chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Writeuphelp
Writeup from AMN 6(1):

Sample No.: ALHA81251

Location: Allan Hills

Field No.: 1248

Weight (gms): 158.0

Meteorite Type: LL3 Chondrite

 

Physical Description: Roberta Score

Thin, black, shiny fusion crust covers half of this flat sample. The exterior appears to have been polished, and the broken surfaces show abundant chondrules as large as 0.5 cm in diameter. The interior exposed by chipping has weathered to a deep reddish-brown, obliterating any structure present. Dimensions: 6.5 x 6 x 2.5 cm.

Petrographic Description: Brian Mason

The section shows a close-packed aggregate of chondrules and chondrule fragments, up to 3 mm in maximum dimension. Most of the matrix is black and opaque, with small grains of olivine and pyroxene; the black matrix appears to be carbonaceous, with small amounts of troilite and nickel-iron (largely weathered to limonite). A wide variety of chondrule types is present, including barred olivine, granular olivine and olivine-pyroxene, and fine-grained pyroxene. Clear glass is present in barred olivine chondrules. Microprobe analyses show olivine and pyroxene with variable compositions: olivine, Fa1-Fa29, mean Fa14 (per cent mean deviation FeO is 64); pyroxene, Fs2-Fs28 , mean Fs13 (per cent mean deviation FeO is 72). Clear glass in a barred olivine chondrule has the following composition (weight per cent): SiO2 61.4, Al2O3 23.5, FeO 1.7, MgO 2.0, CaO 0.4, Na2O 4.8, K2O 1.6, TiO2 1.1, MnO 0.01. The highly variable composition of olivine and pyroxene and the texture indicate Type 3. The small amount of nickel-iron suggests LL group. Hence the meteorite is tentatively classified as an LL3 chondrite.

Data from:
  MB76
  Table 2
  Line 773:
Origin or pseudonym:Main icefield
Mass (g):158
Class:LL3.2/3.4
Weathering grade:B/C
Fayalite (mol%):1-29
Ferrosilite (mol%):2-28
Comments:26Al=45±2; 76004 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° 40' 47"S, 159° 20' 11"E)
Note: the NHM and MetBase coordinates are 9.4 km apart

Statistics:
     This is 1 of 38940 approved meteorites from Antarctica (plus 5051 unapproved names)
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