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Northwest Africa 15500
Basic information Name: Northwest Africa 15500
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 15500
Observed fall: No
Year found: 2022
Country: (Northwest Africa)
Mass:help 467 g
Classification
  history:
Meteoritical Bulletin:  MB 111  (2023)  Lunar
Recommended:  Lunar    [explanation]

This is 1 of 108 approved meteorites classified as Lunar.   [show all]
Search for other: Lunar meteorites
Comments: Approved 20 Dec 2022
Writeuphelp
Writeup from MB 111:

Northwest Africa 15500 (NWA 15500)

(Northwest Africa)

Purchased: Mar 2022

Classification: Lunar meteorite

History: Purchased online in March 2022 by Craig Zlimen froma meteorite dealer in Algeria.

Physical characteristics: Single stone with no visible fusion crust. A slice of the interior reveals the stone to be divided in half into two different rock types.

Petrography: (D. Sheikh, Cascadia) Specimen represents a dimict breccia comprised of two distinct (but genetically related) lithologies separated by a sharp contact: Lith A) A feldspathic fragmental breccia composed of mm-sized angular to subangular lithic and mineral clasts set within a fine-grained matrix. Clast lithologies identified in this sample include anorthosites, norites, olivine norites, troctolites, pink spinel troctolites, pink spinel anorthosites, and impact melt clasts; clasts lithologies are predominantly Mg-suite in composition, with minor input from lunar ferrous anorthosite. Accessory phases include ilmenite, SiO2-rich glass, and merrillite. Lith B) A clast-poor troctolitic impact melt composed of compositionally zoned olivine and minor high-Ca pyroxene dendrites (Av. grain size ~10 µm, and unzoned plagioclase laths (mix of both cracked and smooth, Av. grain size ~0.5 mm). Clast lithologies identified include anorthosites, pink spinel anorthosites, and troctolites. Accessory phases include SiO2-rich glass and ülvospinel.

Geochemistry: Lith A [Olivine (Fa17.8±12.1, range Fa4.4-53.3, Fe/Mn=85±14, n=76), Low-Ca Pyroxene (Fs23.9±13.8Wo3.4±1.2, range Fs10.5-52.2Wo0.8-4.6, Fe/Mn=55±8, n=23), Pigeonite (Fs33.0±10.1Wo10.7±3.3, range Fs19.1-56.6Wo6.3-17.0, Fe/Mn=55±7, n=16), High-Ca Pyroxene (Fs15.8±6.6Wo38.1±5.3, range Fs5.8-29.6Wo26.0-45.7, Fe/Mn=50±10, n=15), Calcic Plagioclase (An96.5±0.6, range An94.9-98.0, n=79), Pink Spinel (Cr#=3.9±0.2, Mg#=85.5±1.3, n=70)]; Lith B [Olivine (Fa21.6±5.8, range Fa9.1-30.7, Fe/Mn=79±11, n=35), Low-Ca Pyroxene (Fs15.7±0.8Wo4.3±0.1, range Fs15.2-16.3Wo4.3-4.4, Fe/Mn=57±4, n=2), High-Ca Pyroxene (Fs27.4±12.9Wo39.5±2.7, range Fs8.6-37.4Wo36.8-43.2, Fe/Mn=46±5, n=4), Calcic Plagioclase (An95.8±0.8, range An94.4-97.9, n=40), Pink Spinel (Cr#=3.9±0.1, Mg#=82.0±1.3, n=19)].

Classification: Lunar (dimict breccia). The unusual presence of bonifide pink spinel anorthosite clasts that contain pink spinel compositionally similar to those measured by the Moon Mineralogy Mapper imaging spectrometer (M^3) suggest derivation of this specimen from a previously unsampled region on the lunar surface.

Specimens: 20.2 g at Cascadia, main mass with Craig Zlimen.

Data from:
  MB111
  Table 0
  Line 0:
Place of purchase:online
Date:P Mar 2022
Mass (g):467
Pieces:1
Class:Lunar
Shock stage:high
Weathering grade:low
Fayalite (mol%):17.8±12.1; 21.6±5.8
Ferrosilite (mol%):23.9±13.8, 33.0±10.1, 15.8±6.6; 15.7±0.8, 27.4
Wollastonite (mol%):3.4±1.2, 10.7±3.3, 38.1±5.3; 4.3±0.1, 39.5±2.
Classifier:D. Sheikh, Cascadia
Type spec mass (g):20.2
Type spec location:Cascadia
Main mass:Craig Zlimen
Comments:CML 1625; submitted by Daniel Sheikh
Institutions
   and collections
Cascadia: Cascadia Meteorite Laboratory, Portland State University, Department of Geology, Room 17 Cramer Hall, 1721 SW Broadway, Portland, OR 97201, United States; Website (institutional address; updated 28 Oct 2011)
Catalogs:
References: Published in Gattacceca J., McCubbin F. M., Grossman J. N., Schrader D. L., Chabot N. L., D’Orazio M., Goodrich C., Greshake A., Gross J., Joy K. H., Komatsu M. and Miao B. (2023) The Meteoritical Bulletin, No. 111. Meteoritics & Planetary Science 58, 901–904. ?
Find references in NASA ADS:
Find references in Google Scholar:
Photos:
CreditPhotos
Photos uploaded by members of the Encyclopedia of Meteorites.
    (Caution, these are of unknown reliability)
Robert Smart      
Public domain photographs:
Daniel Sheikh                     
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 9806 approved meteorites from (Northwest Africa) (plus 1855 unapproved names)

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