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Northwest Africa 16812
Basic information Name: Northwest Africa 16812
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 16812
Observed fall: No
Year found: 2024
Country: Algeria
Mass:help 313 g
Classification
  history:
Recommended:  Ureilite    [explanation]

This is 1 of 672 approved meteorites classified as Ureilite.   [show all]
Search for other: Achondrites, Ureilites
Comments: Approved 6 Jul 2024
Writeuphelp
Writeup from MB 113:

Northwest Africa 16812 (NWA 16812)

Algeria

Find: 2024

Classification: Ureilite

History: Found in Algeria in 2024; later purchased by Matthew Stream, who sent 20.2 grams to Cascadia for classification.

Physical characteristics: Single stone with weathered fusion crust.

Petrography: (D. Sheikh, Cascadia) Sample displays an overall recrystallized texture comprised of mm-sized olivine grains (most of which are polycrystalline and comprised of smaller recrystallized grains ~10 microns in size meeting at ~120° triple junctions) displaying Mg-rich reduced rims, and polycrystalline low-Ca pyroxene (interstitial to olivine, original grain boundaries ~1 mm, comprised of smaller compositionally zoned recrystallized grains ~15 μm in size meeting at ~120° triple junctions). Accessory phases identified include graphite, Fe-Ni metal (primarily along olivine grain boundaries and/or alongside low-Ca pyroxene), troilite, and chromite; subcalcic augite inclusions (<15 microns in size) occur interstitial to recrystallized olivine and low-Ca pyroxene grains. Vesicles are present throughout the sample (primarily concentrated within polycrystalline low-Ca pyroxene).

Geochemistry: Olivine (Fa12.6±4.8, range Fa0.9-19.8 (Fa18.4-19.8 in olivine cores, Fa0.9-9.5 along olivine rims depending on specific grain), CaO (wt. %) = 0.3±0.1, Cr2O3 (wt. %) = 0.6±0.1, Fe/Mn = 24±9, n=39), Low-Ca Pyroxene (Fs9.2±4.1Wo3.8±1.6, range Fs2.3-14.6Wo2.0-6.9, Cr2O3 (wt. %) = 0.9±0.1, Fe/Mn = 17±8, n=28), Subcalcic Augite (Fs8.5±4.6Wo31.1±2.4, range Fs1.1-12.5Wo27.1-33.8, Al2O3 (wt. %) = 1.0±0.7, TiO2 (wt. %) = 0.2±0.1, Cr2O3 (wt. %) = 1.2±0.4, Fe/Mn = 14±8, n=8).

Classification: Ureilite (recrystallized).

Specimens: Cascadia has 17.9 g in one slice, along with a polished thin section and material in an epoxy brick; main mass with Matthew Stream.

Data from:
  MB113
  Table 0
  Line 0:
Date:2024
Mass (g):313
Pieces:1
Class:Ureilite
Shock stage:high
Weathering grade:moderate
Fayalite (mol%):12.6±4.8
Ferrosilite (mol%):9.2±4.1, 8.5±4.6
Wollastonite (mol%):3.8±1.6, 31.1±2.4
Classifier:D. Sheikh, Cascadia
Type spec mass (g):20.2
Type spec location:Cascadia
Main mass:Matthew Stream
Comments:CML 1771; Matt 2; 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 Meteoritical Bulletin, no. 113, in preparation (2024)
Find references in NASA ADS:
Find references in Google Scholar:
Geography:

Algeria
Coordinates:Unknown.

Statistics:
     This is 1 of 1376 approved meteorites from Algeria (plus 31 unapproved names) (plus 4 impact craters)

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