Nova 018

(unknown)

Purchased: 2014

Classification: Ureilite

History: Purchased by D. DGregory at the Denver mineral show in September 2014.

Physical characteristics: (S.Korchinos, UTorG,ROM; V.Di Cecco, ROM) Total mass of pieces is 2.1 kg, with the largest piece having mass of 1.79 kg. Remainder of mass is divided among 12 smaller fragments. The sample is mostly covered by a dark, regmalypted fusion crust. Cracks and exposed surfaces are weathered and rusty. Specimen is very hard and difficult to cut with a diamond saw.

Petrography: (S. Korchinos, UTorG,ROM; V. Di Cecco, ROM) The thin section is composed mostly of coarse-grained olivine with medium-grained, mm to sub-mm pigeonite grains. The silicates exhibit clear reduction rims surrounding their cores. The interstitial matrix and veins are carbon-rich and composed mostly of graphite and numerous nano-diamonds, confirmed using Raman, EPMA and SEM imaging. The interstitial phases appear very dark to opaque when viewed under both plane-polarized and cross-polarized transmitted light.

Geochemistry: Mineral compositions and geochemistry: Oxygen isotopes: analyses of two subsamples were conducted at OkaU by R. Tanaka and E. Nakamura. The analyses gave δ¹⁷O = 4.224, 4.161; δ¹⁸O = 8.648, 8.512; and Δ¹⁷O = -0.331, -0.323 (all values in per mil). Bulk Composition: The olivine cores have Fa_24.1±2.3 (N=43) and their bulk chemistry includes CaO = 0.35 ± 0.12 (N=43), Cr₂O₃ = 0.65 ± 0.23 (N=43), and MnO = 0.42 ± 0.03. The pyroxene cores have Fs_20.6±1.0Wo_10.2±0.2 (N=24) and their bulk chemistry includes CaO = 5.18 ± 0.09 (N=24), Cr₂O₃ = 1.24 ± 0.09 (N=24), MnO = 0.39 ± 0.02

Classification: Achondrite (ureilite). High shock, low weathering.

Specimens: One thin section and the smaller fragments are held at the ROM. The main mass is held by DGregory.