Classification: Mesosiderite A3 S-low / W-low
Place/Time: 2020 in Adrar, Algeria
Mass: 4988+20kg
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.
Classification: Mesosiderite 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.
NOTE: Slice carefuly prepared from both sides, etched and preserved with paraloid.
