Northwest Africa
Found 2004
Achondrite (acapulcoite)
A 68 g mostly crusted, partial stone was purchased in Erfoud in October 2004. Description and classification (T. Bunch and J. Wittke, NAU): recrystallized into polygonal and subhedral grains with the exception of large orthopyroxene grains (up to 3 mm) that poikilitically enclose olivine; heavily fractured, variable grain size, and heterogeneous distribution of phases. Modal analyses (vol. %): orthopyroxene, 44; olivine, 41; FeS, 6; metal (and Fe-oxides), 5; plagioclase, 3 and minor merrillite, Ca-pyroxene and chromite. All silicates have very homogeneous compositions; olivine, Fa13.1 (FeO/MnO = 26); orthopyroxene, Fs12.2Wo2.7 (FeO/MnO = 13.9); plagioclase, An21.9; metal, Ni = 6.7 wt. % Ni. Oxygen isotope analyses are consistent with winonaites, mineralogy and mineral compositions are more consistent with lodranite assemblages. Weathering grade is W2/3 with ferric Fe staining; shock level is S2. Specimens: type example, 13.7 g, NAU: main mass, Strope/Farmer.
Morocco or Algeria
Found 2003
Achondrite (acapulcoite)
History: A 386 g broken stone with weathered fusion crust (part of a larger ~7.5 kg mass found in 2003) was purchased in Erfoud, Morocco, in 2004 for N. Oakes.
Petrography: (T. Bunch and J. Wittke, NAU; A. Irving, UWS) The specimen is recrystallized into homogeneous polygonal and subhedral grains with a grain size of <1 mm and an approximately equal distribution of phases.
Composition: Olivine (Fa8.0; FeO/MnO = 16-19 [n=25]), orthopyroxene (Fs8.4Wo2.4; [n=17]), plagioclase (An18.3-21.0Or2.8-3.4), chromite ((Cr/Cr+Al) = 0.85; Mg/(Mg+Fe) = 0.41). Troilite, schreibersite, and kamacite are also present.
Oxygen isotopes: (D. Rumble, CIW) Replicate analyses by laser fluorination gave δ17O = 1.71, 1.69; δ18O = 5.05, 5.04; Δ17O = -0.953, -0.973 (all ‰).
Classification: Achondrite (acapulcoite); low shock, moderate weathering.
Specimens: A 21 g type specimen and one polished thin section are on deposit at NAU. Oakes holds the main mass.
Reference
Rumble, D., III, Irving, A. J., Bunch, T. E., Wittke, J. H. and Kuehner, S. M. (2005), Discrimination of acapulcoites and lodranites from winonaites. Abstr. 68th Met. Soc. Mtg., #5138.
Algeria
Find: 2005
Achondrite (acapulcoite)
History and physical characteristics: A dark brown, 222 g, partially crusted stone was purchased in Erfoud, Morocco, in November 2005.
Petrography: (J. Wittke and T. Bunch, NAU; A. Irving, UWS) Recrystallized homogeneous, polygonal to subhedral grains <0.8 mm in size.
Mineral compositions and geochemistry: Olivine (Fa14.5±0.2; FeO/MnO = 30.5, MnO > 0.02 wt. %), orthopyroxene (Fs13.3±0.2Wo3.0; FeO/MnO = 17), diopside (Fs6.8Wo41.9; FeO/MnO = 12), plagioclase (An17.4), Fe,Ni rich metal (Ni = 22.5 wt. %). FeS is also observed.
Oxygen isotopes: (D. Rumble, CIW) Multiple analyses of different samples of the rock by laser fluorination are δ17O = +0.78 and +0.97, δ18O = +2.94 and +3.25, Δ17O = -0.764 and -0.743 (all ‰).
Classification: Achondrite (acapulcoite).
Type specimen: A 20.1 g sample is on deposit at NAU. Turecki and Reed hold the main mass.
Northwest Africa
Find: 2006
Achondrite (acapulcoite)
History and physical characteristics: A 63g 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 microns-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/(Cr+Al) = 0.69, 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. Mr. Stefan Ralew holds the main mass.
| ID | Location | Date | Mass (g) | State | Olivine | Pyroxenes | Feldspar | Comments |
|---|---|---|---|---|---|---|---|---|
| NWA 2699 | Erfoud, Morocco | 2005 | 1294 | S1, W3 | Fa8.2±0.2 | Fs9.1±0.2Wo3.0 | An23.8 | paired with NWA 2656 photograph below) |
| NWA 2714 | Erfoud, Morocco | 2005 | 100 | S1, W3/4 | Fa8.1 | - | An22.2 | chromite, Cr/(Cr+Al) = 0.85; paired with NWA 2656 (photograph below) |
| NWA 2866 | Erfoud, Morocco | 2005 | 213 | S1, W3 | Fa8.2±0.2 | opx Fs9.3±0.2; cpx Fs4.2Wo43.5 | An24.5Or2.8 | chromite, Cr/(Cr+Al) = 0.70; paired with NWA 2656 (photograph below) |
