Northwest Africa 6542 (NWA 6542)

(Northwest Africa)

Purchased: 2005

Classification: Enstatite chondrite (EL6)

History: A small fragment was purchased at the Bologna Avis Fair by Romano Serra.

Physical characteristics: A single dark brown piece of 15 g with no fusion crust and traces of staining.

Petrography: Vanni Moggi Cecchi, Giovanni Pratesi, Stefano Caporali (MSP): The overall texture is characterized by very rare indistinct chondrules set in a fine-grained matrix mainly composed of pyroxene. Several multiple subparallel and anastomozing thin veinlets, about 150 μm long, filled with iron oxides/hydroxides can be observed in the thin section in reflected light. Enstatite accounts for about 90% of the total volume. Relict chondrules are mainly RP type, with minor PP, and range from 0.3 to 0.7 mm in diameter. Opaque phases are mainly altered kamacite (with 0.7 wt.% Si) and troilite (with 5.6 wt. % Ti). Accessory phases are alabandite, schreibersite and daubréelite as blades in troilite. The presence of alabandite and Si content of kamacite point to a classification as EL chondrite.

Geochemistry: Enstatite (En_97.8Wo_1.5), plagioclase (An_14.1Or_4.2).

Classification: Enstatite chondrite (EL6); S1; W3. This specimen is probably paired with NWA 4415 and NWA 4416.

Specimens: A total of 3 g of sample, one polished thin section and a block are on deposit at MSP. OAM holds the main mass.