Sample No.: ALHA77299

Location: Allan Hills

Field No.: 77123030

Weight (gms): 260.7

Meteorite Type: H3 (tentative)

Physical Description:

Sample ALHA77299 is nearly tabular. A thin, glassy, spotty fusion crust covers approximately 10-15% of the meteorite's surface, however, it is mostly confined to the T surface. The remaining surfaces are smooth and medium brown. Much of the meteorite's surface that is not covered by fusion crust is glassy. The B surface has only small glassy areas and is appreciably iron-oxide stained. Specimen is ~9.5x5.5x3.5 cm. Stone was difficult to chip. The broken surface produced by chipping contains chondrules and fresh metal.

Petrographic Description: Brian Mason

The section shows a closely-packed mass of chondrules (0.15-1.5 mm diameter) and irregular crystalline aggregates with interstitial nickel-iron and troilite and a relatively small amount of matrix. A considerable variety of chondrules is present, many of granular or porphyritic olivine with transparent to turbid interstitial glass; other types include fine-grained pyroxene, medium-grained olivine and polysynthetically-twinned clinopyroxene, and barred olivine. The section is stained yellow-brown with limonitic material, with small areas (up to 0.4 mm across) of red-brown limonite along one edge (near surface?). Microprobe analyses show olivine ranging in composition from Fa11 to Fa21, with a mean of Fa16; the pyroxene is low-calcium (CaO=0.4-1.2%), with a range in composition from Fs15 to Fs20 and a mean of Fs18. The mean composition of the olivine and the amount of nickel-iron suggest H group, so the meteorite is tentatively classified H3; however, certain assignment of group should await further investigation.