Famoso meteorite diogenite NWA 7831 Acondrite Meteorite - 1 g - (1)
N. 83879673
Fetta di Ureilite NWA 13135 Acondrite Meteorite - 1.72 g - (1)
N. 83879673
Fetta di Ureilite NWA 13135 Acondrite Meteorite - 1.72 g - (1)
Physical characteristics: Dark-brown individual with well preserved fusion crust. The interior of the meteorite is grayish, with granular texture.
Petrography: (P. Yu. Plechov, FMMR). Petrographic observation of a polished section shows that the meteorite is composed of coarse-grained olivine (up to 2 mm) and fine pigeonite (size up to 400 µm). Olivine grains are Fo80.5 and elevated CaO (0.38±0.05 wt.%, n=13) and Cr2O3 (0.78±0.06 wt.%, n=13) abundances. No high-Ca pyroxene or orthopyroxene were observed. Pigeonite has 5.5-6.0 wt.% CaO. Saw-tooth, carbon-rich veins cross the meteorite. Veins or vein fragments with thicknesses of about 50 μm are composed by graphite (without diamond). Thinner veins of about 20 μm thickness contain kamacite with schreibersite rims and troilite-daubreelite intergrowths. Narrower veins, up to 10 μm in thickness, are mostly filled with iron hydroxides. Olivines have reduced rims with very tiny ( µm) drops of iron (without Ni) and more magnesium than the cores (up to Fo87.8). These features are typical for olivine-pigeonite, main group ureilites (monomict ureilites). Irregularly shaped cracks and the absence of other features of impact indicate the sample has a very weak shock stage. Kamacite is partially replaced by iron hydroxides, whereas sulfides and silicates are fresh.
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