Northwest Africa 4741 (NWA 4741)

(Northwest Africa)

Found: unknown

Classification: Ungrouped achondrite

History: One single stone purchased in Erfoud, June 2005.

Physical characteristics: The stone measures 40×20×15 mm and weighs 20 g. It is 70% covered with dark brown fusion crust and discrete regmaglypts. The interior is light gray and fine grained.

Petrography: (A. Jambon, O. Boudouma, D. Badia, UPVI; J-A Barrat and M. Bohn, UBO). Dominant olivine and low-Ca pyroxene exhibit thin, iron-enriched rims at the contact with interstitial glass. Troilite, chromite, kamacite, taenite, and augite are also present. The sample is partly brecciated and shock melted. Some crystals of olivine and pyroxene have serrated overgrowths a few micrometers wide. Mode (vol %): olivine = 24%; pyroxene = 64%; glass = 6 %; voids 4%; accessories 2%.

Geochemistry: Olivine: Fo₉₇, FeO/MnO = 20. Enstatite: En₉₄Fs₅Wo₁, FeO/MnO = 19. Major elements by ICP-AES and  trace element composition by ICP-MS (J.-A. Barrat UBO): silicic-feldspathic glass: SiO₂ = 76-68 wt%; Al₂O₃ = 6-13 wt%; FeO = 4-7 wt%; CaO = 2-10 wt%; Na₂O = 1-4 wt%; K₂O = 0.7-0.2 wt%. Bulk composition: SiO₂ =52.7 wt%; MgO = 37.3 wt%; FeO = 6.06 wt%; NiO = 0.1 wt%. Incompatible elements abundances close to chondritic. Light REE depleted pattern with La/Lu = 0.57 × chondritic. Negative Eu anomaly, Eu*/Eu = 0.60. Anomalous ratio of Na/K = 3.0 (by wt). Oxygen Isotopes (R. Greenwood and I. Franchi, OU): δ¹⁸O = 4.99 ‰, δ¹⁷O = 2.64 ‰, Δ¹⁷O = 0.047 ‰.

Classification: Achondrite (ungrouped). Only marginally weathered. Shock melted.

Specimens: A total sample mass of 5 g and one polished section are on deposit at UPVI. An anonymous collector holds the main mass.