Northwest Africa 10517 (NWA 10517)

(Northwest Africa)

Purchased: 2004 Feb

Classification: Ordinary chondrite (L3-6)

History: Purchased by Richard Pugh in February 2004 from a Moroccan trader at the Tucson Gem and Mineral Show.

Physical characteristics: Partly fusion crusted individual with brownish weathering patina on broken surfaces.

Petrography: (A. Ruzicka and K. Farley, Cascadia) Breccia with ~7% metal overall, composed of an intimate mixture of mineral and chondrule fragments with diverse (type 3-6) characteristics and some larger clasts; areas between chondrules and clasts largely composed of smaller clasts. BSE imaging of thin section shows that most of the rock is composed of type 4-6 lithologies, with equilibrated olivine, and coarse plagioclase (commonly 20-70 μm and up to 120 μm long), interspersed with sharply-defined glass-bearing chondrules and chondrule fragments. One area prominently shock-blackened.

Geochemistry: (K. Farley and A. Ruzicka) Dominated by equilibrated olivine (median Fa_24.4, N=68) and low-Ca pyroxene (median Fs_21.0, N=67) but also containing more varied olivine (Fa_4.1-38.8) and low-Ca pyroxene compositions (Fs_2.9-26.1). Average of mixture including both equilibrated and more varied compositions is olivine (Fa_24.4±6.1, N=68), low-Ca pyroxene (Fs_18.6±5.6Wo_1.5±1.1En_80.0±6.3, N=67), high-Ca pyroxene (Fs_9.9±1.7Wo_42.9±2.8En_47.2±2.9, N=19), plagioclase (Ab_81.3±2.7Or _7.2±1.4An_11.4±2.1, N=19), alkali feldspar (Ab_59.3±2.0Or_30.7±0.0An_10.0±2.1, N=2).

Classification: L3-6 finely intermixed genomict breccia. Type 5-6 implied by common equilibrated olivine and coarse feldspar; type 3 implied by presence of magnesian olivine and glass in chondrules and fragments.

Specimens: Cascadia holds the entire sample, which consists of 85.3 g in two pieces, one polished thin section, and a potted butt.