Sample No.: ALHA77304

Location: Allan Hills

Field No.: B77123114

Weight (gms): 650.4

Meteorite Type: LL3 Chondrite

Physical Description:

Dull, brownish-black fusion crust, approximately 0.5 to 1 mm thick, covers all but the W surface of this angular, 9.5x8.0x6.5 cm, sample. On the W surface and areas where the fusion crust has been plucked away, greenish matrix material with numerous chondrules and irregular lithic clasts ranging from light to dark gray and as much as 1 cm in diameter, is exposed. A fracture on the B surface appears to penetrate the entire stone. When the meteorite was cleaved in half, haloing effects were observed around some of the inclusions in the interior of the stone. There is no obvious weathering rind.

Petrographic Description: Brian Mason

The section shows a closely-packed aggregate of chondrules, with a minimum amount of fine-grained matrix; a little troilite and nickel-iron is present in the matrix. Some of the chondrules are unusually large, ranging up to 3 mm in diameter. The commonest types are barred and porphyritic olivine chondrules with interstitial glass; some of the glass is isotropic and transparent, but most is turbid and partly denitrified. Polysynthetically twinned clinopyroxene occurs with the olivine in some chondrules. A 6x3 mm enclave, consisting of closely-packed idiomorphic olivine crystals with interstitial turbid brown glass, is present at one edge of the section. Brown limonitic staining pervades the section. Microprobe analyses show olivine (Fa18-27, average Fa24) and pyroxene (Fs13-19, average Fs15) of variable composition; the olivine in the enclave has uniform composition, Fa25. A few grains of calcic plagioclase, averaging An77, were noted. The low content of nickel-iron and troilite suggest LL group, and the wide range of olivine and pyroxene compositions type 3, so the meteorite is tentatively classified LL3; however, certain assignment of group may require additional investigation.