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Lewis Cliff 87002
Basic information Name: Lewis Cliff 87002
     This is an OFFICIAL meteorite name.
Abbreviation: LEW 87002
Observed fall: No
Year found: 1987
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 6.9 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 11(2)  (1988)  Eucrite
AMN 17(1)  (1994)  Eucrite-Mg-rich
Meteoritical Bulletin:  MB 76  (1994)  Eucrite-Mg-rich
NHM Catalogue:  5th Edition  (2000)  Eucrite-Mg rich
MetBase:  v. 7.1  (2006)  Eucrite-mmict
Antarctic Meteorite Newsletter:  AMN 36(2)  (2013)  Howardite
Meteoritical Bulletin:  MB 102  (2013)  Howardite
Recommended:  Howardite    [explanation]

This is 1 of 382 approved meteorites classified as Howardite.   [show all]
Search for other: Achondrites, HED achondrites, and Howardites
Comments: Field number: 4418
Revised 30 Aug 2013: Reclassification from AMN 36(2)
Writeuphelp
Writeup from AMN 11(2):

Sample No.: LEW87002

Location: Lewis Cliff

Weight (g): 6.9

Field No.: 4418

Dimensions (cm): 2.5 x 1.5 x 1

Meteorite Type: Eucrite, Mg-rich

 

Macroscopic Description: René Martinez

This pebble is an achondrite with black, vitric fusion crust covering about 70% of its surface. It has an igneous texture overall, but appears crushed. Very light colored pyroxene and plagioclase are present.

 

Thin Section (,4) Description: Brian Mason

The section is made up of clasts, up to 1.2 cm across, of pyroxene with minor plagioclase, in a comminuted groundmass of these minerals. One clast, 6x3 nun, consists of an ophitic intergrowth of plagioclase and pyroxene. Pyroxene composition is Wo3Fs31; plagioclase composition averages An92 (Na2O 0.8-1.0%). The ophitic clast contains both orthopyroxene (Wo5Fs31) and augite (Wo44Fs12) with some intermediate compositions: plagioclase is An91. While the bulk composition approximates that of a howardite, this meteorite lacks the diogenetic pyroxene characteristic of the howardites; it is probably best classified as an Mg-rich eucrite.

 


Writeup from AMN 36(2):
Sample Number LEW 87002
Newsletter 11,2
Location Lewis Cliff
Field Number 4418
Dimensions 2.5 x 1.5 x 1
Weight 6.92
Original Classification Eucrite, MG-Rich
Updated Classification Howardite
Mineral Composition (%Fa &  %Fs)
Ferrosilite (mol%): 12-31
Weathering
Ae
Fracturing
A
Macroscopic Description - René Martinez
This pebble is an achondrite with black, vitric fusion crust covering about 70% of its surface. It has an igneous texture overall, but appears crushed. Very light colored pyroxene and plagioclase are present.
Thin Section Description (,4) - Brian Mason
The section is made up of clasts, up to 1.2 cm across, of pyroxene with minor plagioclase, in a comminuted groundmass of these minerals. One clast, 6x3 nun, consists of an ophitic intergrowth of plagioclase and pyroxene. Pyroxene composition is Wo3Fs31; plagioclase composition averages An92 (Na2O 0.8-1.0%). The ophitic clast contains both orthopyroxene (Wo5Fs31) and augite (Wo44Fs12) with some intermediate compositions: plagioclase is An91. While the bulk composition approximates that of a howardite, this meteorite lacks the diogenetic pyroxene characteristic of the howardites; it is probably best classified as an Mg-rich eucrite.
Reclassification Notes (36,2)
LEW 87002, initially classified as a Eucrite, Mg-rich (Antarctic Meteorite Newsletter 11(2), page 29, 1988), is a fragmental breccia containing mm-sized clasts of low-Ca pyroxene, a mafic clast with subophitic texture, and a matrix composed mostly of low-Ca pyroxene and plagioclase. Low-Ca pyroxenes in the matrix, the margins of orthopyroxene clasts, and from the margin of the mafic clast are relatively uniform in Fe/Mg and have compositions of Wo2.5-3.5En64.4-66.3Fs31.0-32.1. High-Ca pyroxene compositions in the same petrologic settings are Wo40.4-42.0En43.4-45.4Fs14.3-15.3. The most magnesian orthopyroxene in the core of a mm-sized clast is Wo0.8En77.0Fs22.2, the most ferroan low-Ca and high-Ca pyroxenes from the mafic clast core are Wo2.5En58.1Fs39.4 and Wo43.0En41.2Fs15.8. Olivine compositions are Fo60.6, plagioclase compositions range from An94.6Ab5.2Or0.2 to An87.0Ab12.4Or0.6. The bulk rock composition determined by Warren et al. (2009; GCA 73:5918) has a subchondritic Eu/Sm and major element composition consistent with a mixture of diogenite:basaltic eucrite of ~65:35. LEW 87002 is a howardite exhibiting an exceptional degree of post-assembly metamorphism that caused large-scale Fe-Mg exchange.
Antarctic Meteorite Images for Sample LEW 87002
North View of Sample LEW 87002  South View of Sample LEW 87002  Thin Section Photograph of Sample LEW 87002 in Plane-Polarized Light  Top View of Sample Splits for Sample LEW 87002 
Bottom View of Sample LEW 87002  Thin Section Photograph of Sample LEW 87002 in Cross-Polarized Light 
Data from:
  MB76
  Table 2
  Line 3580:
Origin or pseudonym:South Lewis Cliff
Mass (g):6.9
Class:Eu "mg"
Weathering grade:Ae
Ferrosilite (mol%):12-31
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 11(2) (1988), JSC, Houston
Published in Antarctic Meteorite Newsletter 36(2) (2013), JSC, Houston
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (84° 17'S, 161° 5'E)
     Recommended::   (84° 21' 50"S, 161° 16' 47"E)
Note: the NHM and MetBase coordinates are 9.3 km apart

Statistics:
     This is 1 of 40129 approved meteorites from Antarctica (plus 4494 unapproved names)
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