Hier nochmal ganz was Leckeres, und ebenfalls mit perfekter Knopf-Form: NWA 4816, kleine Hauptmasse eines Acapulcoiten. Allerdings hatte ich mal gehört, dass an der Klassi noch gearbeitet wird, weil das Steinchen so schräg ist, dass wohl einige Zweifel bestehen, dass es ein Acap ist. Könnte eher vielleicht ein ungruppierter Achondrit sein. Ich selbst hatte solch einen Meteoriten auch vorher noch nicht gesehen.
Northwest Africa 4816
Northwest Africa
Find: 2006
Achondrite (acapulcoite)
History and physical characteristics: A 63 g stone was purchased in Erfoud, Morocco, in 2006 by Stefan Ralew. The partial stone has moderate surface weathering of broken areas. Small metal spherules and droplets protrude through a thin, residual fusion crust.
Petrography: (T. Bunch and J. Wittke, NAU) Highly enriched in kamacite metal, mineral modes (in vol%) are orthopyroxene, 33; olivine, 25; kamacite, 24; diopside, 15, plagioclase and felsic glass, 3 and FeS + chromite, 1.0. Silicates are fine-grained (mean = 0.60 mm) and show euhedral to subhedral grain outlines. Orthopyroxene contains micrometer-sized glass blebs. Rare, round to ovoid granular clusters may represent relict chondrules. Shock level is S2 and the weathering grade is W1.
Mineral compositions: Olivine, Fa5.6; FeO/MnO = 12. Orthopyroxene is Fs6.2Wo2.1, FeO/MnO = 9 and diopside is Fs2.8Wo45.5, FeO/MnO = 7. Plagioclase is An66, chromite cr# = 69 and kamacite contains 6.1 wt% Ni. Felsic glass is (in wt%): SiO2, 51.2; Al2O3, 20.3; CaO, 10.8; Na2O, 2.6; K2O, 0.8; MgO, 12.0 and FeO. 3.1.
Classification: Achondrite (acapulcoite).
Type specimen: A 12.4 g sample is on deposit at NAU. S. Ralew holds the main mass.