Sample No.: LEW85320

Location: Lewis Cliff

Weight (g):  ~110224

Field No.: 3164

Dimensions (cm): 61 x 48 x 27

Meteorite Type: H5 Chondrite

Macroscopic Description: Roberta Score

Dull thin black fusion crust with abundant oxidation haloes covers this entire oriented specimen. Shallow regmaglypts are present on each surface except for the bottom. Some regmaglypts contained Antarctic soil. This was collected and given split number 2. LEW85320 is moderately fractured and many of these fractures are lined with crusty and powdery evaporite deposit. Seven hundred milligrams was scraped from the surface and given split number 3. A chip for classification purposes was taken from an inconspicuous area and yielded a highly weathered sample. This most likely is not representative of the weathering or condition of the interior of the entire stone.

Thin Section (,4) Description: James L. Gooding and Brian Mason

This section, which represents the outer 1.5 cm of the specimen, displays ordinary chondritic texture with brecciation. The ferromagnesian chondrule population includes all of the common textural types and most chondrules are readily distinguished from the matrix. However, chondrule pyroxenes are not dominantly monoclinic and chondrule mesostases are mostly crypto-crystalline and birefringent. In addition, there were few, if any, signs of primitive rims on chondrules and the chondrite matrix was mostly a translucent to transparent, granular assemblage of olivine and pyroxene.

Brecciation in this particular sample is most conspicuously displayed as a light/dark contrast between the outer (toward fusion crust) and inner halves of the section. The dark area appears to be enriched in fine-grained matrix (possibly including an enrichment in sulfides) relative to the light area. Although the section is stained with Fe-oxide weathering products of Antarctic origin, the light/dark contrast is probably a feature of pre-terrestrial origin.

A preliminary modal analysis (230 points) of the total section gave 85 vol. % silicates, 11% Ni-Fe metal, and 4% sulfides. Electron microprobe analyses (by B. Mason) showed nearly homogeneous olivine (Fa19) and pyroxene (Fs16). On the basis of texture and composition, the specimen is classified as an H5 chondrite.