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Northwest Africa 7304
Basic information Name: Northwest Africa 7304
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 7304
Observed fall: No
Year found: 2009
Country: (Northwest Africa)
Mass:help 272 g
Meteoritical Bulletin:  MB 101  (2012)  Ureilite
Recommended:  Ureilite    [explanation]

This is 1 of 670 approved meteorites classified as Ureilite.   [show all]
Search for other: Achondrites, Ureilites
Comments: Approved 9 Jul 2012
Writeup from MB 101:

Northwest Africa 7304 (NWA 7304)

(Northwest Africa)

Purchased: Sept 2009

Classification: Ureilite

History: Samples were donated to Cascadia by Mr. Fred Olsen in June, 2010.

Physical characteristics: The rock has a blunt nosecone shape. Fusion crust with radial flow lines emanating from the nose covers ~70% of the specimen. The interior is a relatively uniform dark-gray color.

Petrography: (A.Ruzicka and M. Hutson, Cascadia) An olivine-rich rock (>75%) with low-Ca pyroxene, graphite laths to 1 mm, and Fe-oxide and hydroxide minerals (hematite, goethite, and common hematite-magnetite mixtures). Ca-sulfate is rarely present in veins. Olivine-rich and pyroxene-rich regions are ~1 mm in diameter. Olivine-rich areas are partly recrystallized (shock stage S6) and have recrystallized domains showing one dominant lineation, but are mainly composed of small (<10 μm diameter) subhedral olivine grains with interstices between olivine (<3 μm wide) filled by low-Ca pyroxene, high-Ca pyroxene, and chromite. Interstitial regions between millimeter-sized olivine areas are rich in pyroxene, symplectic Fe-oxide and hydroxide phases, and graphite, the latter partly replaced by Fe-oxide minerals.

Geochemistry: (A. Ruzicka and M. Hutson, Cascadia) Fine-grained, olivine-rich areas far from graphite contain relatively ferrous olivine (Fa22.3±0.3, Fe/Mn = 49±11 at., n=28) and low-Ca pyroxene (Wo4.4±1.5 Fs21.2±1.0, n=10), whereas closer to graphite, olivine (Fa8.1±2.5, Fe/Mn = 17±4 at.%, n=11) and low-Ca pyroxene (Fs12.4±1.8Wo2.8±0.9, n=9) are more magnesian.

Classification: Achondrite (ureilite). Partly shock-recrystallized and melted. Metal is largely replaced by Fe-oxide weathering products but silicates were largely unaffected by weathering.

Specimens: 22.5 g, one polished butt, and one thin section are on deposit at Cascadia. Mr. McKenzie holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Denver
Date:P Sept 2009
Mass (g):272
Shock stage:high
Weathering grade:medium
Fayalite (mol%):22.3, 8.1
Ferrosilite (mol%):21.2, 12.4
Wollastonite (mol%):4.4, 2.8
Classifier:A. Ruzicka, M. Hutson, Cascadia
Type spec mass (g):22.5
Type spec location:Cascadia
Main mass:Mr. Ronnie McKenzie, Pretoria, South Africa
Comments:Field numbers RM-3 and CML0614; submitted by A. Ruzicka
   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. 101, MAPS 50, 1661, September 2015
Find references in NASA ADS:
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     This is 1 of 9806 approved meteorites from (Northwest Africa) (plus 1855 unapproved names)

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