Northwest Africa 5217

Morocco

Find: 2007

Achondrite (aubrite)

History and physical characteristics: A 39.1 g complete and fully crusted stone was found in Morocco in 2007 and given to the present owner at the Tucson Gem and Mineral Show in January 2008.

Petrography: (T. Bunch and J. Wittke, NAU) The fine to medium-grained (<1.2 mm) unbrecciated, cumulate-textured stone is composed essentially of enstatite with interstitial Si-bearing kamacite; sulfides (troilite, daubreelite, brezinaite, oldhamite, alabandite, niningerite, caswellsilverite), graphite, plagioclase, a silica phase, and schöllhornite, a weathering product of caswellsilverite. Weathering grade is low.

Mineral compositions: (EMPA analyses, all in wt%) Enstatite is En_99.4Fs_0.2Wo_0.4; metal is Si-rich kamacite (Ni = 5.8–6.6; Si = 3.9–4.5); Oldhamite: S = 38.7, Ca = 59.2, Cr = 1.4, Mn = 1.2; brezinaite: S = 46.0, Cr =54.1; caswellsilverite: S = 45.3, Cr = 38.4, Na = 14.7, Fe = 0.7; troilite: Cr = 2.68, Ti = 3.38; plagioclase: An₁₇Or_3.7; and schöllhornite: S = 46.0, Cr = 37.3, Fe = 1.1 (remainder is oxygen and hydrogen).

Classification: Achondrite (aubrite).

Type specimen: A total of 8.5 g and one thin section are on deposit at NAU. The holder of the main mass is anonymous.