Northwest Africa 13599 (NWA 13599)

Morocco

Find: 2018

Classification: HED achondrite (Howardite)

History: A single stone weighing 50 g was found in 2018 by an anonymous finder in Morocco and purchased in March 2019 at the Bologna Fair by Lucian Cojocaru

Physical characteristics: The main mass is partially covered by a black, shiny fusion crust with several cracks.

Petrography: (V.Moggi Cecchi, L.Fabrizi, G.Pratesi, UniFi): The thin section analyzed shows a polymict breccia with a basaltic lithology (of eucrite composition), and an orthopyroxene-rich lithology with minor olivine (orthopyroxene of diogenite composition), and mineral fragments set into a more fine-grained clastic matrix. Eucrite and diogenite lithologies are found in approximately equal abundances. A large (1 mm) clast consisting of a very fine intergrowth of olivine, silica and plagioclase mixed with larger high-Ca pyroxene is visible; large orthopyroxene and diopside crystals, ranging in width from 600 to 1000 µm are common, with minor olivine crystals and very large (600-1000 μm) clasts of elongated diopside-orthopyroxene crystals; scattered low-Ca pyroxene crystals, 400-800 µm in size, with fine (5-10 μm) pigeonite exsolution lamellae are visible. A large (200x800 µm) silica polymorph crystal is also present. Minor phases are FeNi metal and troilite, with rare ilmenite and chromite grains.

Geochemistry: EMP (V. Moggi Cecchi, L. Fabrizi, G. Pratesi, UniFi); Olivine in Ol/silica intergrowth (Fa_75.9±1.6Fs_24.1±1.4; n=5; Fe/Mn = 38.3±0.2); Olivine crystals (Fa_58.4±1.2Fs_41.6±1.3; n=8; Fe/Mn = 46.6±0.2); Low-Ca pyroxene crystals (Fs_23.3±0.3En_74.1±0.7Wo_2.6±0.3; n=7; Fe/Mn = 29.5±0.2); Low-Ca lamellae in exsolved orthopyroxene (Fs_55.2±1.4En_40.8±1.2Wo_4.0±0.3; n=5; Fe/Mn = 28.9±0.2); Diopside exsolution lamellae in orthopyroxene (Fs_29.6±1.2En_29.0±0.9Wo_41.8±1.1; n=7; Fe/Mn = 27.2±0.3); Calcic plagioclase An_86.0±0.5Or_0.7±0.5, n=8.

Classification: Howardite with medium degree of shock and medium degree of weathering.

Specimens: Lucian Cojocaru owns the main mass, weighing 40 g; the type specimen, weighing 10 g, and one thin section are on deposit at MSN-FI (Inventory # I-3615)