Northwest Africa 14600 (NWA 14600)

(Northwest Africa)

Purchased: 2021

Classification: Carbonaceous chondrite (C3.00, ungrouped)

Physical characteristics: Individual meteorites with well-preserved fusion crust, showing a network of contraction cracks.

Petrography (K. Metzler, IfP): Carbonaceous chondrite, consisting of small chondrules, chondrule fragments, AOAs, and some CAIs, embedded in a black, fine-grained matrix. The mean apparent chondrule size is 133±145 µm (35-1196 µm; n=124). Mostly type I chondrules, but some type II chondrules and chondrule fragments occur. Several chondrules are rimmed by dust mantles. Point counting (n = 400) on BSE images revealed ~29 area% (vol%) fine-grained matrix, including dust mantles. Nearly all preexisting metal and sulfide appears to be replaced by pure magnetite. Point counting (n = 400) on BSE images revealed ~9 area% (vol%) magnetite, which roughly corresponds to ~15 wt% magnetite. Some tiny relicts of very Ni-rich metal (65 at% Ni) and sulfides (troilite and pentlandite) are present in the centers of magnetite grains. Some dust mantles are crosscut by magnetite veins.

Geochemistry: Mineral compositions and geochemistry: Mean value of randomly chosen olivine grains: Fa_6.1±11.8 (Fa_0.2-45.1; n=25). Mean value of randomly chosen low-Ca pyroxene grains: Fs_2.4±1.9Wo_1.2±0.8 (Fs_0.8-9.0Wo_0.2-3.5; n=27).

Classification: Carbonaceous chondrite based on the predominance of type I chondrules and CAI occurrence. Petrologic type 3 based on the strong chemical variation of olivine and pyroxene. This meteorite has textural and microchemical characteristics nearly identical to that of NWA 13689 (C3.00-ung). NWA 13689 and NWA 14600 were bought in Nouakchott within a year. They show very similar mean apparent chondrule sizes and matrix fractions and contain uniquely high amounts of magnetite (~15-18 wt%). Furthermore, based on the very characteristic fusion crust with contraction cracks, the individual stones of both meteorites are indistinguishable from each other. From this it can be proposed that NWA 13689 and NWA 14600 meteorites are likely paired.

Specimens: Largest individual: 121.0 g.