Sidi El Habib 001 (SEH 001)        24.298°N, 3.745°W

Bordj Badji Mokhtar, Algeria

Find, possible fall: 2020 Dec

Classification: Ordinary chondrite (H5, anomalous)

History: On December 20, 2020, a bright fireball was witnessed in western Algeria by people prospecting for additional material of the Erg Chech 002 meteorite. After searching for two days a group of fresh fusion crusted stones was found at a location close to the Mali border at 24.298°N, 3.745°E and near a well named Hassi el Kounti. All of the collected material was purchased by Ben Hoefnagels in May 2021 from two Moroccan dealers.

Physical characteristics: Fresh fusion crusted stones with broad and shallow regmaglypts. Largest stone is 1.1 kg. Broken surface shows light-colored clasts in a matrix of light grey material. This grey material contains relatively abundant, to 1-mm, bright blue to purple grains of halite. Density of a 34 g stone comprising the two lithologies is 3.77 g/cm3, determined by the glass bead method. Magnetic susceptibility log χ (× 10^-9 m³/kg) = 5.17.

Petrography: (L. Garvie, ASU) A sawn and polished 8 × 6 cm slice shows subhedral light-colored clasts, to 2 cm, in a light-grey matrix. Purple to blue crystals are locally abundant in the light-grey matrix: a powder XRD pattern of these crystals is dominated by reflections for halite and minor sylvite. Well-formed, though sparse, chondrules scattered through-out the clast and matrix lithologies, 601±403 micron (n=26), and separated by coarse-grained mineral and chondrule fragments. Chondrules dominated by PO, rare BO, and rare RP. Some unusual chondrule types present including one dominated by olivine-feldspar-chromite in the matrix lithology, and several Na-Al-Si-rich chondrules in the light-colored clast. Element mapping shows the NaCl to be present only in the grey-matrix lithology at all spatial scales from the mm-sized grains to sub-μm inter-grain films. The halite and sylvite are anhedral, though internally show well-developed cubic cleavage, and give the appearance of euhedral grains. A typical 4 × 4-mm-sized area of the halite-rich matrix contains ~8 areal% NaCl. High-resolution BSE images of the matrix show local regions with bright intergranular "veins" that are rich in Fe-Ni-Cl with little to no Na. A 1-mm subhedral ferroan sphalerite with a rim of troilite occurs in one of the probe mounts from the matrix lithology. The grain contains ~23 wt% Fe, close to the composition for rudashevskyite. Examination of the hand specimens shows several ferroan sphalerite grains in the matrix lithology: XRD of one of the grains confirms the sphalerite structure. Interchondrule feldspar is variable in size, though typically 5 to 20 μm. Merrillite and apatite are common in the clasts as grains to 0.5 mm (total 0.2 areal%). Some merrillite grains have veins and mantles of apatite. Element mapping of the light-colored clast shows several Cl hot-spots that are rich in Fe and Ni, but lack Na. Apatite and merrillite grains are more sparse and smaller in the matrix material.

Geochemistry: (L. Garvie, ASU): Halite-bearing lithology Fa_19.4±0.5, range Fa_18.5-20.4, FeO/MnO=37.5±3.5, n=9; Fs_16.8±0.3Wo_1.46±0.08, n=14. The halite contains up to 0.1 wt% K, 0.7 wt% Fe, and 0.3 wt% Br. The sylvite contains up to 0.3 wt% Na and up to 0.1 wt% Br. The ferroan sphalerite contains between 21.1 and 23.8 wt% Fe. Light-colored clast 19.2±0.3, range 18.7-19.5, FeO/MnO=37.8±2.2, n=10; Fs_16.7±0.1Wo_1.44±0.08, n=12.

Classification: H5 (breccia, anomalous). The pervasive presence of primary alkali halides in this meteorite is anomalous, and previously recognized only in Zag and Monahans (1998).

Specimens: ASU - 319.2 g and eight 1-inch polished rounds. The rest is with Ben Hoefnagels.