El Sauz        26°36’25.1"N, 98°44’42.0"W

Texas, United States

Confirmed fall: 2023 Feb 15

Classification: Ordinary chondrite (L6)

History: (L. Welzenbach Fries, RiceU): At 17:22 CST (23:22:40), 2023 February 15, a fireball was seen over the Rio Grande Valley of southern Texas. Nine eyewitnesses reported a bolide (AMS Event 1036-2023), with sonic booms reported by hundreds to local media and police covering an area from McAllen in the SE, west to Laredo and south into Mexico. Signatures of falling meteorites in NOAA NEXRAD Doppler radar reflectivity data overlay the flat scrubby ranch land and windmill farms of the Rio Grande valley of south Texas. The first radar signature appears at 23:23:40 UTC at an altitude of 14.7 km and the last appears at 23:38:53 UTC and 6.7 km altitude. Total duration is 15 min 13 s, an unusually long period marked by initial detection of unsorted meteorites and late detection of slow-falling dust. Dark flight modeling using the Jörmungandr model suggested meteorites landed in an east to west-trending line that terminates near the village of El Sauz, Texas. The search party included Linda Welzenbach Fries, Marc Fries, Robert Ward, Ricky Gonzalez Sr., Ricky Gonzalez Jr., and Phil Mani. The first sample (444 g) was found by R. Ward on 18 February near a fence line. Three more samples 1269, 756, and 1151 g plus a 26 g fragment were recovered from Feb 19-20. A sixth fragmented stone (1171 g total) that impacted a mature mesquite tree was recovered a week later. Four additional stones weighing 107, 81, 40, and 17 g were recovered by Sonny Clary and Terry Scott from the neighboring ranch, bringing the total mass to 5062 g. Additionnal stones brought the total mass to 5230 g. First samples were found on Coates Ranch just east of El Sauz, TX, situated midway on a line between Edinburgh in the SE, Laredo in the NW, and due north of Rio Grande City. Other stones are reported to have been collected from a bordering ranch along the eastern boundary, including one within line-of-sight from the first stone recovered. All stones were found near the projected fall line in areas where the grass was sparse and short. All recoveries to date appear to be confined between two ranch properties.

Physical characteristics: (L. Welzenbach Fries, RiceU): All intact stones are >95% fusion crusted. Fusion crust is matte black with few chondrule outlines. The fragment (used for classification) is flat, 50% covered in fusion crust on one side, exposed interior on the other showing a light gray friable matrix with poorly defined chondrules with bright, unoxidized finely disseminated metal, but is without veins or any obvious brecciation.

Petrography: (L. Welzenbach Fries, Rice University): The groundmass is recrystallized, highly fractured, with varying degree of chondrule preservation, and only a few larger barred olivine chondrules with well-defined margins. Chondrule sizes range 400-700 µm in diameter. Feldspar grains range from 20 to 100 µm. In BSE imaging, there are isolated areas with micro-faults, melting and recrystallization. Accessory minerals are chromite, ilmenite, and merrilite. Olivine and pyroxene exhibit moderate mosaicism; shock stage is at least S4.

Geochemistry: (L. Welzenbach Fries, G. Costin, T. Sun, RiceU, J. Friedrich, FordhamU): EPMA analyses-Olivine (Fa_25.59±0.4, N=44); Low-Ca pyroxene (Fs_21.1±0.3,Wo_1.5±0.3, N=60); high-Ca pyroxene (Fs_{8.2± 0.3},Wo_43.9±0.47, N=7), feldspar (Ab_83.7±1.5, An_10.4±0.5, Or_5.84±1.3, N=22); chromite Fe/Fe+Mg=0.91±0.1, N=13, Cr/Cr+Al=0.85±0.14, N13. Taenite is more abundant than kamacite; kamacite (Fe=93.4-95.9, Ni = 3.4-6.0, N=10), taenite (Fe=66.8±0.74, Ni = 33.23±0.67, N=5), tetrataenite (Fe=46.12±1.0, Ni = 54.1±1.12, N=5), troilite (Fe = 36.1±0.52, S = 36.3±0.2, N=8). Oxygen isotopes (T. Sun, RiceU): analyses of acid-washed subsamples by laser fluorination gave, respectively δ¹⁷O = 3.712; δ¹⁸O = 4.93; Δ¹⁷O = 1.148 per mil. Siderophile elements in El Sauz (Re-Pd below, n=10) have a mean normalized abundance of 0.89±0.19, which is most consistent with the L chondrite range of values (averaging at ~0.75 × CI and Mg normalized). Magnetic susceptibility (L. Welzenbach Fries) measured by SM30 is log χ (× 10^-9 m³/kg) = 5.19.

Classification: Ordinary chondrite (L6). The texture, chemistry and oxygen isotope data are consistent with L ordinary chondrite, petrologic type 6.

Specimens: Type specimens- 23.52 g mass, 0.4 g chips/fines, PS, PTS and potted butt, TCU. Coates Ranch owner retains 4 individuals including the main mass; 1269, 1151, 756, and 444 g. P. Mani and R. Ward split a fragmented stone that hit a mesquite bush (1171 g). Additional stones found on a neighboring property include 107, 81, 40, 17 g remain with Clary and Terry Scott.