Northwest Africa 13935 (NWA 13935)

(Northwest Africa)

Purchased: April 2018

Classification: Ordinary chondrite (LL3-4)

History: Cascadia was contacted by Aziz Habibi, who said that he obtained this stone in Morocco in April 2018.

Physical characteristics: Physical Characteristics: The slice examined shows a weathered exterior colored orange to dark brown. On the cut face, angular dark clasts are set in an orange-brown colored host lithology. The largest dark clast has two edges (1 cm × 1.5 cm long) in contact with the host lithology; the other two edges of this clast are truncated by the edge of the sample. The host lithology contains numerous well-defined chondrules, many of them yellow to orange set in an orange-brown background. Three easily seen bleached chondrules are visible within this lithology. In the largest dark clast, distinct light brown chondrules, chondrule fragments, and metal and sulfide grains are visible amidst a black-colored background. Four smaller dark clasts (one 0.6 cm long, the others <=0.3 cm long) are visible within the host lithology.

Petrography: (M. Hutson, A. Ruzicka, Cascadia): The host lithology contains tightly packed chondrules. Numerous dark veins with calcite centers cut across the host lithology, and stop at the contact with the dark clast. BSE images show that the veins are composed of a mix of calcite and Fe-bearing weathering products. Offsets in chondrules and silicate grains are sometimes seen on either side of some veins. BSE images show apparent replacement of pyroxene by olivine. The largest dark clast is comprised of a few large chondrules and partial chondrules set in a dark matrix composed of small chondrule and mineral fragments. Shock stages for both lithologies, based solely on olivine deformation, indicate a shock stage of S4 for the host, and a shock stage of S2 for the largest dark clast.

Geochemistry: Mineral compositions and geochemistry: Olivine Fa_28.7±0.8, N=22 (host), Fa_27.7±9.5, N=37 (clast) ; Low-Ca pyroxene: Fs_18.5±4.8Wo_1.4±1.7, N=19 (host), Fs_14.3±9.1Wo_0.9±0.9, N=10 (clast).

Classification: LL3-4 genomict breccia based on mineralogy, mineral compositions and textures. Host is LL4 base on mineral chemistry. Clast is LL3 based on mineral chemistry, texture, and metal content which is lower than host.

Specimens: Cascadia holds 20.0 g in one piece, as well as a polished thin section and material in a stub.