Sample No.: ALHA77140

Location: Allan Hills

Field No.: Y77123124

Weight (gms): 78.62

Meteorite Type: Tentatively L3 Chondrite

Physical Description:

The specimen is roughly conical shaped. The basal portion is irregular and appears to be a broken surface. The remainder of the meteorite's surface is only slightly pitted and is suggestive of a fusion crust. The entire meteorite is a dark reddish-brown with considerable rust-like staining. The extensive weathering of the stone has apparently removed or altered most of the fusion crust.

Petrographic Description: Brian Mason

The section examined consists of an elliptical non-chondritic enclave, 8x5 mm, completely enclosed in highly chondritic material. .The enclave consists of polysynthetically-twinned clinoenstatite (somewhat variable composition, averaging Wo0.2Fs7En93) poikilitically enclosing irregular to globular isotropic or weakly anisotropic masses. These masses have variable composition (SiO2 59-83%, FeO 15-31%, MgO 5-9%, K2O 2.7-4.3%, Na2O 0.6-2.6%, Al2O3 ~0.3%, CaO, TiO2, <0.1%); they appear to be devitrified glass, and some analyses are close to that of merrihueite. The enclave has a little interstitial nickel-iron and troilite. The chondritic portion consists of a close-packed mass of chondrules, with a relatively small amount of fine-grained matrix. Chondrules range in diameter from 0.2 to 2 mm, and exhibit a variety of form and structure; the component consists of granular aggregates of olivine and polysynthetically-twinned clinopyroxene, sometimes with a little interstitial glass. Both olivine and clinopyroxene are highly variable in composition. Olivine ranges from Fa8 to Fa44, with an average of Fa25; pyroxene ranges from Fs2 to Fs17, with an average of Fs7 and a low calcium content, averaging 0.2% CaO. Troilite and nickel-iron are interstitial to the chondrules, and part of the nickel-iron has weathered to limonitic material. The highly variable composition of olivine and pyroxene indicates a type 3 chondrite, and the mean composition of the olivine and the amount of nickel-iron suggest L group, so the meteorite is tentatively classified L3; however, certain assignment of group should await further investigation.