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Pecora Escarpment 82500
Basic information Name: Pecora Escarpment 82500
     This is an OFFICIAL meteorite name.
Abbreviation: PCA 82500
Observed fall: No
Year found: 1982
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 90.9 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 6(2)  (1983)  LL6
AMN 7(2)  (1984)  CV4
AMN 9(4)  (1986)  C4
AMN 17(1)  (1994)  CK4-5
Meteoritical Bulletin:  MB 76  (1994)  CK4-5
NHM Catalogue:  5th Edition  (2000)  CK4-6
MetBase:  v. 7.1  (2006)  CK4/5
Antarctic Meteorite Newsletter:  AMN 31(1)  (2008)  CK4/5
AMN 41(1)  (2018)  CK3
Recommended:  CK3    [explanation]

This is 1 of 42 approved meteorites classified as CK3.   [show all]
Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 3), CK chondrites, CK3 chondrites, and CV-CK clan chondrites
Comments: Revised 3 Jun 2019: Reclassified in AMN 41(1)
Writeuphelp
Writeup from AMN 6(2):

Sample No.: PCAA82500

Location: Pecora Escarpment

Field No.: 2723

Weight (gms) : 90.9
Meteorite Type: LL6 Chondrite

 

Physical Description: Carol Schwarz

This specimen is very unusual looking. It is extremely fragmented with numerous cavities, some extending through the thickness of the sample. The cavities were filled with ice and snow when the sample was removed from the freezer. Several patches of fusion crust are present. The exterior surfaces are a dark gray color with the fresher areas exhibiting a light gray to yellowish color. Inclusions (chondrules?) have been exposed on the exterior surface. The interior contains much white evaporite deposit along with areas of yellowish weathering residue. A dark gray fine-grained matrix is visible in less weathered areas as are minute metal flecks and a few yellowish dots of oxidation. Dimensions: 7 x 5 x 2.8 cm

 

Petrographic Description: Brian Mason

The section snows a single porphyritic olivine chondrule, diameter 3.6 mm, in an aggregate of turbid anhedral olivine grains averaging 0.1 mm. Small amounts of troilite and nickel-iron are present, the nickel-iron being largely weathered to brown limonite. Microprobe analyses gave olivine composition Fa31; no pyroxene was found, but occasional grains of plagioclase ranging in composition from An20 to An40 were analyzed. The meteorite is classified as an LL6 chondrite.


Writeup from AMN 41(1):
PCA 82500: reclassification

Currently a CK5, but should be a CK3. The observations supporting the low petrologic grade include (1) lack of ilmenite exsolution rom magnetite, a property typically seen in type 3 CKs and (2) olivine zoning observed in BSE within the largest chondrule in the type section. Taken together, these sug-est classification as a type 3.
Data from:
  MB76
  Table 2
  Line 4834:
Origin or pseudonym:Main
Mass (g):90.9
Class:CK4-5
Weathering grade:Be
Fayalite (mol%):31
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 41(1) (2018), JSC, Houston
Published in Antarctic Meteorite Newsletter 6(2) (1983), JSC, Houston
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (85° 38'S, 68° 42'W)
     Recommended::   (85° 41' 8"S, 68° 48' 27"W)
Note: the NHM and MetBase coordinates are 5.9 km apart

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