- Meteorite Type: Brachinite
- Meteorite Weight: 12.4 grams
- Approximate Measurements: 59 mm x 56 mm x 1 mm
- Additional Information: Found by Meteorite Men co-host Steve Arnold! Laboratory-prepared slice
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Brachinite, Found in Chile, 2018
WRITEUP FROM THE METEORITICAL BULLETIN:
El Médano 395 (EM 395) 24°53’S, 70°23’W
Find: November 2018
Classification: Primitive achondrite (Brachinite)
History: A single 2288 g stone was recovered near the top of a large hill from the desert pavement by Steve Arnold in November 2018 on a meteorite hunting expedition in the El Médano region of the Atacama Desert.
Physical characteristics: The sample is dark brownish-orange in color, has a tabular shape and covered by a weathered patina. A cut face shows the interior is composed of dark-reddish interlocking crystals.
Petrography: Description and classification (A. Love, App): Sample displays a protogranular xenomorphic texture composed of 300-2500 µm olivine (93 vol%) and diopside (5.5 vol%), oxidized Fe metal, chromite (0.64 vol%), sulfide (0.25 vol%) and plagioclase (0.57 vol%). Diopside has irregularly shaped grain boundaries.
Geochemistry: (A.Love, App) Olivine: Fa33.3±0.4, Fe/Mn=71.6, Mg#67, CaO=0.1Wt%, N=16; High-Ca pyroxene: Fs8.0±0.5Wo46.8±0.8 Fe/Mn=47.2, Mg#85, N=10; Plag: An47.3Or0.0; Cr-Spinel: Cr#66, Mg#26, Fe/Mn=61.7. Oxygen isotopes (K. Ziegler, UNM): analyses of 3 acid-washed subsamples by laser fluorination gave, respectively, δ17O = 2.170, 2.020, 2.329 ; δ18O =4.582, 4.290, 4.897 ; Δ17O = -0.250, -0.245, -0.256 (all per mil). Oxygen isotopes are depleted in 17O and plot in the region below the TFL.
Classification: Textures, mineral compositions, oxygen isotopes and magnetic susceptibility suggest this is a brachinite.
Specimens: Steve Arnold holds the main mass. One slice weighing 20.45 g and a polished thin section and mount are on deposit at App.