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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
Recommended:  Lunar    [explanation]

This is 1 of 103 approved meteorites classified as Lunar.   [show all]
Search for other: Lunar meteorites
Comments: Approved 20 Dec 2022
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:
  Table 0
  Line 0:
Place of purchase:online
Date:P Mar 2022
Mass (g):467
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
   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)
References: Published in Meteoritical Bulletin, no. 111, in preparation (2022)
Find references in NASA ADS:
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Photos uploaded by members of the Encyclopedia of Meteorites.
    (Caution, these are of unknown reliability)
Robert Smart      
Public domain photographs:
Daniel Sheikh                     

     This is 1 of 9429 approved meteorites from (Northwest Africa) (plus 1876 unapproved names)

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