from The Meteoritical
Bulletin, No. 108
Northwest Africa 2420
Purchase: 2017 Jan
Mass: 395 g
meteorite was exported from Morocco to Tucson where it was purchased by N.
Physical characteristics: Dark grey
matrix with lighter gray to white clasts up to 7 mm.
Warren, UCLA) Overall, the sample consists preponderantly of
plagioclase, although mafic silicates are comparably abundant in some
clasts. The texture is a fine-grained and obviously polymict breccia, but
hard to precisely classify. The groundmass is especially fine grained and
locally vesicular. But most of the rock consists of diverse lithic and
mineral clasts that survived the breccia-forming process. The clasts
include earlier-generation impact melt products akin to "crystalline
lunar spherules". Glass (i.e., clearly regolithic) spheroids are not
found. Several patches of brown, swirly, vesicular glass suggest a possible
minor component of regolithic derivation, but the brown color is less
diagnostic in a meteoritic find than it would be an Apollo breccia.
pyroxene (11 analyses) is compositionally diverse, e.g., Fs30Wo11,
Fs51Wo9, with average FeO/MnO = 55.9; while 2 augite
analyses are Fs20Wo41 and Fs26Wo40.
Plagioclase (9 analyses) is An95.4-96.8, average An96.1.
The bulk composition, determined by INAA and fused-bead EPMA applied to 2
chips totaling 670 mg, is uncommonly aluminous (31 wt% Al2O3)
even for a lunar highland breccia, and also ferroan with bulk Mg/(Mg+Fe) =
57 mol%. For the middle REE Sm, as a representative incompatible element, the
sample has 0.9 µg/g, and for the arch-incompatible Th, 0.2 µg/g.
highland polymict breccia
mass with Gessler, type specimen at UCLA.