Eucrite
TKW 873 grams. Fall not observed. Found 2013.
Mendy writes:
A fine grained, equilibrated eucrite.
Physical characteristics: Single stone, shiny black fusion crust, saw cut reveals fresh, light-gray, fine-grained groundmass.
Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows a protogranular texture with ~50% pyroxene and 45% plagioclase, grain size 10-100 ìm, many pyroxenes with exsolution lamellae. Accessory silica, ilmenite, and chromite.
Geochemistry: (C. Agee and L. Burkemper, UNM) Low Ca-pyroxene Fs60.6±1.7Wo3.0±1.9, Fe/Mn=33±1, n=14; high-Ca pyroxene Fs27.6±0.6 Wo42.3±0.8, Fe/Mn=34±1; n=7; plagioclase Or0.5±0.0Ab10.9±0.5An88.7±0.5, n=3.
Classification: Achondrite (Eucrite). Equilibrated main group eucrite.
Notes from Dr. Carl Agee: NWA 7874 is a fine grained basalt, thus quickly cooled. It is not considered monomict because it’s texture isn’t dominated by brecciation. It is not considered cumulate either based on the pyroxene compositions which are highly equilibrated, probably due to a second heating like metamorphism.
See more here
|