Glendale        33°41’15.70"N, 112°13’6.80"W

Arizona, United States

Confirmed fall: 26 July 2018

Classification: Ordinary chondrite (L6)

History: (M. Fries, M. Hankey) At 8.22 p.m. local time on 26 July 2018 a meteor traveled from the NW to SE across central Arizona. There were twelve reports in Arizona, most clustered around the Phoenix area, with one eyewitness in north-central Phoenix reporting sonic booms (American Meteor Society event number 2624-2018). This low eyewitness count may be explained because this was both a daytime fireball and the fall occurred among scattered thunderstorms in the Phoenix area. Signatures of falling meteorites can be found in imagery from two nearby weather radars. In the NEXRAD weather radar network operated by NOAA, the KIWA (Phoenix, AZ) radar recorded the fall. The airport radar for Phoenix Sky Harbor Airport (TPHX) also recorded signatures of falling meteorites. The first appearance of falling meteorites on radar occurs at 03:27:24 UTC and 3,710 m above sea level (ASL) in the 0324 UTC data set for the KIWA radar in the 2.4° elevation radar sweep. Signatures consistent with falling meteorites appear in two radar sweeps from the two radars, with a final signature appearing at 03:27:37 UTC. Several days after the meteor event, Mr. Cody Horvath noticed a single, black fusion crusted stone partially embedded in his granite-covered, xeriscaped front garden. The impact of the stone left a small depression in the granitic gravel and fragments of stone and fusion crust were scattered around the depression. The find location is directly under the projected strewnfield for the fall. Further information available at NASA and ASU.

Physical characteristics: (L. Garvie, ASU) An 85.23 g blocky stone covered by relatively thick (~0.5 mm) matte fusion crust. The impact removed several pieces of the fusion crust exposing a light-colored interior. A 4 × 3 cm slice shows a patchy white to light-grey interior studded with small (<1 mm) metal grains and very few recognizable chondrules. The density of a 10.36 g slice is 3.54 g/cm³ (determined using the glass-bead method). The stone is brittle, recrystallized, with a sugary texture.

Petrography: (L. Garvie, ASU) A polished thin section shows a coarsely crystalline rock with a few difficult-to-recognize chondrules. Rock dominated by minerals exhibiting a protogranular texture interspersed with rare recognizable chondrules including PP-RP (1 mm), two BO (0.7 mm and 1.1 mm), and pyroxene-rich (2.2 mm). Feldspar typically 100 to 200 µm, with some grains to 500 µm. Troilite, to 300 µm, single crystal, many grains with abundant shock lamellae. Kamacite, to 500 µm, lacking Neumann bands. Taenite/tetrataenite to 100 µm. Kamacite and taenite grains have a tendency to be equant. Locally abundant <10 µm euhedral to subhedral kamacite, some with triangular, lath, and square outlines. Accessory phosphates dominated by apatites to 500 µm, and chromites to 200 µm. Sparse native Cu grains, to 15 µm, at taenite/kamacite boundaries.

Geochemistry: Olivine - Fa_24.81±0.08, n=11, FeO/MnO=47.3±2.8 Low-Ca pyroxene - Fs_20.9±0.2Wo_1.48±0.24, n=13, FeO/MnO=29.0±1.4 High-Ca pyroxene - Fs_7.2Wo_45.6 and Fs_7.9Wo_44.6 Feldspar - Ab_84.9±0.6An_9.9±0.1, n=11 Taenite/tetrataenite - Ni 42.4±6.0 wt%, range 37.6 to 52.6 wt%, Co 0.14±0.02 wt%, n=7 Kamacite - Ni 5.3±0.4 wt%, Co 0.87±0.08 wt%, n=4 Chromite - Cr/(Cr+Al) = 0.87±0.00, Fe/(Fe+Al) = 0.80±0.00, V₂O₃ to 0.7 wt%, n = 5 Phosphates dominated by apatite with Cl 3.8±0.6 wt%.

Classification: L6. Presence of a few extensively recrystallized chondrules, occurrence of many large feldspar grains, and granoblastic texture indicate extensive thermal metamorphism.

Specimens: 17.06 g at ASU