Gila Mountains        32°41.101’N, 114°24.460’W

Arizona, USA

Found: 20 May 2012

Classification: Ordinary chondrite (H4)

History: One specimen weighing 3.854 kg was recovered by Jason Ira Ryan in May, 2012, from the Arizona desert near the Gila Mountains.

Physical characteristics: One piece, weighing a total of 3.854 kg, was recovered. A dark brown fusion crust, uniformly covering the entire sample, with a total thickness of ~0.5 mm was observed. A thin layer of carbonate material, likely of terrestrial origin, was observed on the surface of the fusion crust. The sample showed no signs of post-fall fractures or damage.

Petrography: (A.J. Lussier, NotreD) Gila Mountains shows a brecciated texture in hand sample, with reddish-brown-to-tan colored, irregularly-shaped clasts (ranging in size from 2-7 mm) set in dark brown/black matrix material; the volume ratio of clasts to matrix is approximately 1:1.5. Chondrules are present in both the clast and matrix material and opaque phases (i.e., oxides and sulfides) are disseminated throughout intra-chondrule areas. Scanning electron microscopy shows that chondrules in the clast material are reasonably well preserved with well-defined edges, whereas chondrules in the matrix are less well preserved, with edges that range from being well- to poorly-defined or ruptured. The cpx:opx ratios of the clast and matrix regions are 3:2 and 2:3, respectively. Throughout the entire sample, pyroxene grain sizes range from 20 to ~150 μm, with the average size being ~70 μm; cpx grains are dominantly equant, whereas opx grains range from equant to elongate. No feldspar grains are visible by petrographic microscope.

Geochemistry: (A. Lussier, NotreD, and I. Steele, UChi) EMPA. Olivine Fa_19.0±0.7, Fe/Mn=39±2, n=124; low-Ca pyroxene Fs_17±1Wo₁, Fe/Mn=23±2, n=110; high-Ca pyroxene Fs_9±3Wo_40±12, Fe/Mn=21±6, n=31; kamacite, Fe_0.92±0.06N_i0.82, n=12; tetrataenite Fe_0.50±0.01Ni_0.50, n=5; taenite Fe_0.74±0.11Ni_0.26, n=6.

Classification: Ordinary chondrite (H4). Weathering grade W1. Shock stage S2.

Specimens: Type specimen, 38 g and a thin section, ROM. Main mass, J. Ryan.