Stone, achondrite, diogenite-olivine
Find: May 2009
TKW: 2.29 kg
Half individual: 426.0 g
This is one of only a handfull meteorites that are classified as olivine-, or harzburgitic diogenite (greater than 40 vol% olivine). Out of the 419 diogenites presently known, only ten qualify as harzburgites (olivine + magnesian orthopyroxene in contrast to conventional / ferroan orthopyroxene diogenites). NWA 7370 is also quite high in chromite (15 wt%). Chromite can be seen as black notches protruding from the crust. Due to its higher melting point, the chromite resisted atmospheric ablation better than the matrix.
Write up (Meteoritical Bulletin 101):
History: Four meteorites were discovered by an anonymous finder east of Agaraktem, Mali, in May 2009.
Physical characteristics: Four almost complete individuals totaling 2290 g.
Petrography: (R. Bartoschewitz, Bart) Polycrystalline olivine clusters (~50 vol%) of idiomorphic to hypidiomorphic cystals (<1 mm, average about 0.1 mm) distributed in schlieren-like bands within a matrix of xenolithic to hypidiomorphic pyroxene grains (about 1 mm), with rare intergranular feldspar. Chromite and metal occurs dominantly within pyroxene and olivine grains.
Geochemistry: (R. Bartoschewitz, Bart; P. Appel, B. Mader, Kiel) Pyroxene Fs23.8-25.4Wo2.0-4.4, olivine Fa29.3-30.3, feldspar An76-83Ab1-5. Chromite Al2O3 = 14.4-15.4, TiO2 = 0.9-1.1, MgO = 4.1-4.8; Kamacite Ni = 0.3-1.1, Co = 0.7-0.9 (all in wt%).
Classification: Olivine diogenite, S1, very fresh
The specimen up for sale is the main mass of NWA 7370. With its well-preserved texture, bottle-green matrix and olive drab patina this rare HED achondrite is an exceptional showpiece and unique collection specimen.