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Northwest Africa 16402
Basic information Name: Northwest Africa 16402
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 16402
Observed fall: No
Year found: 2022
Country: (Northwest Africa)
Mass:help 151 g
Meteoritical Bulletin:  MB 112  (2024)  Ureilite
Recommended:  Ureilite    [explanation]

This is 1 of 672 approved meteorites classified as Ureilite.   [show all]
Search for other: Achondrites, Ureilites
Comments: Approved 3 Jan 2024
Writeup from MB 112:

Northwest Africa 16402 (NWA 16402)

(Northwest Africa)

Purchased: Sep 2022

Classification: Ureilite

History: Mr. Jasper Spencer purchased two stones (138 and 13 g) from a Mauritanian dealer in September 2022 via FB Messenger. The dealer stated that the two stones represented one meteorite (they appeared identical and were found near each other) and that they had been found in Mauritania sometime in 2022. Mr. Spencer sent a 27.8 g end cut from the larger stone to Cascadia for classification.

Physical characteristics: Physical Characteristics: The exterior surface of the piece received by Cascadia has an irregular surface and lacks obvious fusion crust. It is dark gray with patches of light orange and tan in low areas. The cut face is medium- to dark-gray, with visible coarse grains up to about 2 mm in length.

Petrography: (B. Agyemang, A. Ruzicka, M. Hutson, Cascadia): In thin section, the sample is comprised of about 75% olivine and about 25% low-Ca pyroxene (pigeonite). Graphite occurs in laths (approximately 0.5 to 1.5 mm across) at grain boundaries. Iron hydroxide veins (weathering) occur in grain boundaries and fractures. Troilite occurs near graphite patches and in iron hydroxide veins. Ni-bearing metal is found near grain boundaries and cracks. Metal grains are largely replaced by Fe-oxide/hydroxide weathering products, but the cores and rims of the silicates appear largely unaffected by weathering. Olivine grains (typically about 1.5 mm across) show evidence of undulatory extinction, planar fractures, and no mosaicism (U-S3). Olivine grains range from anhedral to euhedral in shape, have thin reduction rims, and commonly intersect at triple junctions. Low-Ca pyroxene grains (approximately 1.5 to 2 mm across) display fractures and exsolution lamellae.

Geochemistry: (B. Agyemang, M. Hutson, V. Mugica, J. Laster, A. Ruzicka, Cascadia): Twelve olivine grains and eight pyroxene grains were analyzed by a combination of single points and traverses. Some grains had only one analysis, while others had multiple analyses. Data for each individual grain were averaged so as not to bias the average mineral chemistry towards a grain with a large number of analyses. Rim compositions were obtained for eight of the twelve olivine grains. Olivine cores Fa17.0±0.2, Fe/Mn=35.7±1.6, Cr2O3=0.61±0.05 (wt%), CaO=0.31±0.03 (wt%), N=12 grains; olivine rims Fa6.4-15.0 (range), N=8 grains; low-Ca pyroxene (pigeonite) Fs14.8±0.2Wo7.3±0.1, N=8 grains.

Classification: Ureilite, based on mineralogy, texture, mineral chemistry, and presence of graphite.

Specimens: Cascadia holds 21.1 g in one piece, as well as a polished thin section and material in an epoxy butt; Mr. Jasper Spencer holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:FB Messenger
Date:P Sep 2022
Mass (g):151
Shock stage:U-S3
Weathering grade:moderate
Fayalite (mol%):17.0±0.2, N=12 grains
Ferrosilite (mol%):14.8±0.2, N=8 grains
Wollastonite (mol%):7.3±0.1, N=8 grains
Classifier:B. Agyemang, M. Hutson, V. Mugica, J. Laster, A. Ruzicka, Cascadia
Type spec mass (g):27.8
Type spec location:Cascadia
Main mass:Mr. Jasper Spencer
Comments:Lab number CML 1671; submitted by Melinda Hutson
   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 Gattacceca J., McCubbin F. M., Grossman J. N., Schrader D. L., Cartier C., Consolmagno G., Goodrich C., Greshake A., Gross J., Joy K. H., Miao B. and Zhang B. (2024) The Meteoritical Bulletin, no. 112. Meteoritics & Planetary Science 59, 1820–1823. ?
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     This is 1 of 9829 approved meteorites from (Northwest Africa) (plus 1851 unapproved names)

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