Sample No : ALH84027

Location: Allan Hills

Weight (g) 8.0

Field No.: 1531

Dimensions (cm): 2 x 1.5 x 1

Meteorite Type: LL7(?) Chondrite

Macroscopic Description: Carol Schwarz

Fusion crust, weathered and fractured in places, covers all but one side of this fragment. The remaining surface is brown with a small area of greenish material. The interior is reddish brown to dark gray with metal present.

Thin Section (,3) Description: Glenn MacPherson

This meteorite is an intensely recrystallized chondrite with only a few very faintly preserved barred olivine chondrules that testify to its chondritic heritage. The texture is basically polygonal-granular but is porphyroblastic in some areas. Principal minerals are olivine (uniformly Fa27), coarse plagioclase (An10 Ab85 Or5), diopsidic pyroxene (En49 Fs1O Wo41), orthopyroxene (En75 Fs23 Wo2), chromite, troilite and minor Ni-rich metal. Preliminary analyses suggest that two slightly different orthopyroxenes are present (one with 0.85% CaO and the other with 1.2% CaO). Large metal grains are zoned from cores of approximately 27% Ni to rims of approximately 35% Ni. On a volumetric basis, metal is very subordinate to troilite. Although the olivine composition is transitional between L- and LL-chondrites, the low metal abundance suggests classification as LL, despite the lack of brecciation. The high CaO concentration in orthopyroxene (commonly >1%) and the unusually coarse degree of recrystallization suggests petrologic type 7. Therefore, this specimen is tentatively classified as an LL7 chondrite. Slight local staining of metal particles indicates mild terrestrial weathering. Well-developed fusion crust forms approximately one-half of the perimeter of the section.