Ubá        ~21°07’S, ~42°57’W

Minas Gerais, Brazil

Find: 1960

Classification: Ordinary chondrite (H5)

History: (M. E. Zucolotto, MN/UFRJ): A 36 g sample of the meteorite was found next to an old card labelled "Ubá" in the MNRJ on a date prior to the fire. The piece was spared from the fire because it was at the IGEO/UFRJ for analysis. On the card was written that the meteorite was found in 1960 with an initial total mass of 84.5 g, located at Mineralogy collection of the Faculty of Philosophy of USP, and this sample was donated by Prof. Ruy Ribeiro Franco and labeled "44-MT." The mass given to the MNRJ was 36 g, but only 24.4 g are remaining.

Physical characteristics: The remaining MNRJ sample measures 36.2 × 25.1 × 14.4 mm and weighs 24.4 g. It is an end-piece of a larger stone with a distinct angular edge and shows dark-brown fusion crust. The cut surface exhibits a slightly brownish-gray interior. Microscopically, the meteorite is quite fresh, with metal phase preserved.

Petrography (M. E. Zucolotto, MN/UFRJ and A. Tosi, IGEO/UFRJ): Under optical microscope, two thin sections were analyzed and showed Ubá as an unbrecciated ordinary chondrite containing a light mm-sized clast set within brownish-gray host with generally readily discernible equilibrated chondrules. Composed predominantly of orthopyroxene, olivine, FeNi metal (kamacite), troilite and interstitial albitic feldspar (<50 µm). Minor Ca-rich pyroxene (pigeonite and augite), taenite, and tetrataenite phases occur. Dark and light regions were observed with the same petrologic texture exhibiting a low shock stage S1 to S2 due to the presence of sharp and undulatory extinction of olivine and presence of Newman lines in kamacite. Troilite is essentially unaltered and most metal is fresh with few oxidized grains (W1).

Geochemistry: (A. Tosi, IGEO/UFRJ) Electron microprobe analysis yields: Host: olivine Fa_20.0±0.9 (41); low Ca pyroxene Fs_17.1±0.5Wo_1.4±0.7 (22); Ca-rich pyroxene Fs_12.2±3.6Wo_29.1±15.2 (16); plagioclase Ab_77.7±3.1An_15.9±4.3Or_6.67±3.12 (15), Co in Kamacite 4.82±0.02 mg/g (16). Clast: low-Ca pyroxene Fs_13.8±1.2Wo_1.36±0.7 (10), plagioclase Ab_77.0±1.78An_17.7±2.9Or_5.3±1.57 (10).

Classification: H5 ordinary chondrite. Weathering (W1) and slightly shocked (S1-2)

Specimens: 24.4 g and two thin sections at MNRJ.