Al-Khadhaf        18°22.114’N, 53° 26.001’E

Zufar, Oman

Confirmed fall: 2022 Mar 08

Classification: Ordinary chondrite (H5-6)

History: On the night of 8 March 2022 at 20:15h UTC, the Global Fireball Observatory detected a fireball over Dhofar in southern Oman. The object entered the atmosphere at a velocity of 14 km/s. The event lasted 3.2 s, beginning at an altitude of 67.6 km and ending at 30.2 km. The meteoroid was modeled to have a pre-impact orbit of a = 1.72±0.02 [AU], e = 0.45±0.01, i = 4.36±0.06 [deg]. Its dark flight and fall position were modeled independently by the team from Curtin University (Australia) and by Beat Booz (Switzerland). On 7 Feb 2023, two meteorites were recovered, 395 m apart, after one day of searching by a team of 6 persons, in vicinity of the calculated fall lines (27 and 390 m away from the lines). The coordinates of the larger stone are 18°22.114’N 53° 26.001’E. The smaller stone was found at 18° 22.009’N 53° 25.809’E. The find location is 12.2 km southwest of a small desert camp named Al-Khadhaf. (Al-Khadhaf is Arabic for "camels starting to accelerate and run when reaching an open flat area after passing mountains/dunes")

Physical characteristics: Two specimens with a total mass of 22.065 g were recovered, weighing 13.851 and 8.214 g, respectively. The larger fragment is pyramid-shaped. The smaller piece has an elongated and curved shape. Fusion crust is fresh and dark grey-black. On broken surfaces, chondrules and unaltered silicate minerals are visible, and these surfaces show partial coverage by fusion crust, indicating fragmentation late in flight. Some rust is present around metal and sulfide grains on broken surfaces. Sawn surfaces reveal a brecciated texture containing both mineral and rock fragments.

Petrography: (A. Zappatini, B. Hofmann, E. Gnos) The petrography is based on thin sections of both fragments. The meteorite contains rock fragments of homogeneous composition and single mineral clasts. It is randomly crosscut by shock veins filled with fine-grained mineral clasts and opaque phases. Major minerals are olivine, pyroxene, plagioclase and abundant metal and sulfide. Chromite, merrillite and ilmenite are present in minor quantities. Metal and sulfides are slightly altered to iron (hydr)oxides, predominantly in cracks following the shock veins. The meteorite contains few readily delineated chondrules and chondrule fragments with a diameter of 0.2 - 0.5 mm. Chondrule types include barred olivine, porphyric olivine and radial pyroxene. The matrix is recrystallized and contains mineral clasts of variable grain size. The diameter of feldspar grains ranges from 5 - 50 μm. A large (3 by 5 mm) clast in the larger stone (field name 23_0010) contains coarse plagioclase (>50 μm). Fusion crust is characterized by vesicles and a mesh of fine sulfide veins. Undulous extinction as a shock indicator is prevalent, but no planar fractures were observed.

Geochemistry: Mineral composition and geochemistry: (A. Zappatini) Plagioclase (23_0010) An_11.4±0.5 Or_5.6±0.8 (n=14), plagioclase (23_0011): An_12.1±0.5 Or_5.9±0.2 (n=23), pyroxene (23_0010): Fs_16.6±0.8 Wo_1.3±0.2, Cr₂O₃ 0.13±0.06 wt% (n=25), pyroxene (23_0011): Fs_16.7±0.6 Wo_1.4±0.1, Cr₂O₃ 0.13±0.06 wt% (n=52), olivine (23_0010): Fa_18.3±0.6 (n=39), olivine (23_0011): Fa_18.5±0.5 (n=72), chromite (23_0010): Cr/Cr+Al = 0.84±0.01 Fe/Fe+Mg = 0.83±0.02 (n=7), chromite (23_0011): Cr/Cr+Al = 0.84±0.01 Fe/Fe+Mg = 0.83±0.01 (n=13). Short-lived cosmogenic isotopes (A. Zappatini, S. Lindemann): Both masses were analyzed in the GeMSE gamma spectrometer, yielding activities of 23.7+1.7-1.3 dpm/kg and 26.3+1.7-1.7 dpm/kg for ⁵⁴Mn and 47.4+3.8-2.6 and 46.3+3.4-2.9 dpm/kg for ²²Na (April/May 2023). A provisional terrestrial age of the meteorites was calculated using published initial activities of meteorites which fell during periods of similar solar activity (Braunschweig, Creston, Kamargaon, Soltmany, Torino, Mahbas Arraid, Katol, Mreïra). The resulting median ⁵⁴Mn terrestrial ages are 463 and 416 days, matching the fireball date by ±60 days.

Classification: Mineral compositions, chondrule size and magnetic susceptibility are consistent with an equilibrated H-type ordinary chondrite. The crystalline matrix, chondrule delineation, plagioclase grain size and low chemical variation of olivine and pyroxene indicate a dominant petrologic type 5. The clast in the larger stone containing coarse plagioclase is classified as H6, as it has the same mineral chemistry as the rest of the sample. The meteorite is a H5-6 breccia. The undulous extinction of mineral grains with absent planar fractures points to a shock degree of S2. Slight alteration of sulfide and metal points to a low weathering degree of W1. Based on the freshness of the sample, the find location close to the calculated fall lines and the date of fall calculated from the activities of 54Mn and 22Na, both individuals are related to the fireball observed on 8 March 2022.

Specimens: 5.04 g including two polished thin sections at NMBE, main mass: MHTO.