Description
2.31g part sold in collection box with label/certificate of authenticity.
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Tanezrouft 091 (Tnz 091) 24°15.85’N, 0°09.64’W
Adrar, Algeria
Purchased: 2020
Classification: Mesosiderite
History: Two stones totaling 4988 g were found near Adrar, Algeria. Carlos Muñecas Muñoz purchased the samples from a dealer in Morocco in 2020.
Physical characteristics: Samples are dark brown in color, rounded, and lack fusion crust. Rounded metal nodules protrude through the surface. A cut face shows the interior is composed of a breccia containing: metal grains, cm-sized rounded metal nodules and silicate clasts (up to 4 cm) and mineral grains (up to 0.5 cm).
Petrography: Description and Classification (A. Love, App): Sample is a breccia composed of (vol%): cm-sized rounded metal nodules (3); cm-sized rounded lithic clasts (10) with cumulate and brecciated textures, mineral clasts set within a matrix of poikiloblastic orthopyroxene plagioclase and silicates and metal (~35vol%). Modal percentages (vol%) of silicates (image thresholding of 20 backscattered electron images): orthopyroxene (60), plagioclase (31), olivine (5) and a lath-shaped silica polymorph (4). Matrix pyroxenes are inverted and show blebby and lamellar exsolution. Olivine shows well-developed reaction coronas some of which have replaced entire grains. Grain boundaries between silicates are sutured. Additional minerals are: kamacite, taenite, lath-shaped Si polymorph, apatite, troilite, chromite, trace ilmenite.
Geochemistry: (A. Love, App) Olivine, Fa36.6±7.7 (Fa25.7-44.3, Fe/Mn=40.4±2.5, n=5); zoned low-Ca pyroxene, Fs30.8±2.5Wo2.1±0.7 (Fe/Mn=27.5±1.4, n=6); matrix, Fs37.5±1.3Wo3.2±0.1 (Fe/Mn=23.6±0.5, n=4); high-Ca pyroxene, Fs18.1±1.7Wo40.6±4.2 (n=3). Plagioclase, An92.4±0.4Or0.1±0.1 (n=5).
Classification: Mesosiderite (estimated class) A3. Mesosiderite Class A based on texture, metal abundance, magnetic susceptibility and modal silicate abundance of plagioclase and Opx. Metamorphic class 3 based on recrystallization textures of silicates and absence of pigeonite.
Specimens: Carlos Muñecas (Expometeoritos) holds the 2525 g main mass. A 24.46 g slice and polished mount are on deposit at App.
