Northwest Africa 4236

Northwest Africa

Find: 2004

Achondrite (acapulcoite)

History: A small piece was purchased at the Hamburg Mineral Fair, Germany, from a Moroccan dealer in 2004. An anonymous finder recovered the meteorites from the western part of the Sahara.

Physical characteristics: A 24 g angular fragment with some fusion crust.

Petrography: (J. Schlüter, Ham) Olivine, orthopyroxene, and kamacite are the main components. Rich in troilite and plagioclase with rare chromite grains. Large olivine and orthopyroxene grains (up to 900 µm) are set in a fine-grained matrix. Several relict chondrules (orthopyroxene and rare olivine) up to 2 mm in size are present. Tiny metal inclusions within the relict chondrules are also present. Most metal grains are 100–500 µm.

Mineral compositions and geochemistry: Olivine (Fa_19.19), (range: n = 15, Fa_{18.56–19.62}); orthopyroxene (Fs_16.99), (range: n= 10, Fs_{16.70–17.14}); plagioclase (Ab_81.81Or_5.6), (n = 2); kamacite with Ni = 6.40 wt%; taenite with Ni = 39.43 wt%; chromite = (Fe_0.81Mg_0.17Mn_0.02) (Cr_1.59Al_0.28Fe_0.07,Ti_0.06)O₄ (n = 4).

Classification: Achondrite (acapulcoite); minimal shock and weathering.

Type specimen: A total of 4.9 g is on deposit at Hamb. Herkstroeter holds the main mass.