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Allan Hills A77299
Basic information Name: Allan Hills A77299
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77299
This meteorite may also be called Allan Hills 77299 (ALH 77299) in publications.

Observed fall: No
Year found: 1977
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 261 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 1(2)  (1978)  H3
Meteoritical Bulletin:  MB 76  (1994)  H3.7
NHM Catalogue:  5th Edition  (2000)  H3.7
MetBase:  v. 7.1  (2006)  H3.7
Recommended:  H3.7    [explanation]

This is 1 of 75 approved meteorites classified as H3.7.   [show all]
Search for other: H chondrites, H chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Writeuphelp
Writeup from AMN 4(1):

Sample No.: ALHA77299

Location: Allan Hills

Field No.: 77123030

Weight (gms): 260.7

Meteorite Type: H3 (tentative)

 

Physical Description:

Sample ALHA77299 is nearly tabular. A thin, glassy, spotty fusion crust covers approximately 10-15% of the meteorite's surface, however, it is mostly confined to the T surface. The remaining surfaces are smooth and medium brown. Much of the meteorite's surface that is not covered by fusion crust is glassy. The B surface has only small glassy areas and is appreciably iron-oxide stained. Specimen is ~9.5x5.5x3.5 cm. Stone was difficult to chip. The broken surface produced by chipping contains chondrules and fresh metal.

 

Petrographic Description: Brian Mason

The section shows a closely-packed mass of chondrules (0.15-1.5 mm diameter) and irregular crystalline aggregates with interstitial nickel-iron and troilite and a relatively small amount of matrix. A considerable variety of chondrules is present, many of granular or porphyritic olivine with transparent to turbid interstitial glass; other types include fine-grained pyroxene, medium-grained olivine and polysynthetically-twinned clinopyroxene, and barred olivine. The section is stained yellow-brown with limonitic material, with small areas (up to 0.4 mm across) of red-brown limonite along one edge (near surface?). Microprobe analyses show olivine ranging in composition from Fa11 to Fa21, with a mean of Fa16; the pyroxene is low-calcium (CaO=0.4-1.2%), with a range in composition from Fs15 to Fs20 and a mean of Fs18. The mean composition of the olivine and the amount of nickel-iron suggest H group, so the meteorite is tentatively classified H3; however, certain assignment of group should await further investigation.

Data from:
  MB76
  Table 2
  Line 248:
Origin or pseudonym:Main icefield
Mass (g):260.7
Class:H3.7
Weathering grade:A
Fayalite (mol%):11-21
Ferrosilite (mol%):15-20
Comments:26Al=43±4
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 4(1) (1981), 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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