Sample No.: LEW85313

Location: Lewis Cliff

Weight (g): 191.2

Field No.: 2498

Dimensions (cm): 8 x 5.5 x 4.5

Meteorite Type: Diogenite

Macroscopic Description: Roberta Score

Dull fusion crust covers most of LEW85313 except where large pieces of stone have been plucked out. This feature is abundant and makes this meteorite resemble a piece of Swiss cheese.

A brownish-gray weathering rind extends from less than 1 mm to greater than 1 cm into the interior. The massive gray matrix contains both rounded and irregular inclusions that range in color from white to black. Some oxidation haloes are obvious.

Thin Section (,5) Description: Brian Mason

The section shows orthopyroxene clasts, up to 4 mm across, in a matrix consisting largely of comminuted pyroxene with a small amount of plagioclase. The orthopyroxene clasts show a minor amount of augite exsolution, both blebby and lamellar. Most of the pyroxene has uniform composition, Fs29, but a few more iron-rich grains were analysed; minor constituents are CaO 0.53-2.7%, MnO 0.64-0.80%, Al2O3 0.24-0.91%, TiO2 0.16-0.31%. One grain of diopside, Wo44Fs12, was analysed. Plagioclase composition is An88-91. Accessory amounts of an SiO2 polymorph, probably tridymite, were identified. The meteorite is a diogenite.

Sample No.: LEW85313

Weight (g): 191.2

Dimensions (cm): 8x5.5x4.5

Meteorite Type: Reclassification from diogenite to howardite

Macroscopic Description: Roberta Score

Dull fusion crust covers most of LEW85313 except where large pieces of stone have been plucked out. This feature is abundant and makes this meteorite resemble a piece of Swiss cheese. A brownish-gray weathering rind extends from less than 1 mm to greater than 1 cm into the interior. The massive gray matrix contains both rounded and irregular inclusions that range in color from white to black. Some oxidation haloes are obvious.

Thin Section (,21) Description: Brian Mason

LEW85313 was originally classified as a diogenite on the basis of section 85313,5 (Antarctic Meteorite Newsletter 9 #3, p. 22), Jack Berkley suggested this sample should be reclassified and a new section was made which shows that the meteorite is a howardite, the original section was of an unusually large diogenite clast. LEW85313,21 is a microbreccia of pyroxene clasts (orthopyroxene with minor pigeonite), up to 0.9 mm across, in a comminuted groundmass of pyroxene grains, with minor plagioclase and accessory opaques (troilite and nickel-iron). Microprobe analyses show the following range in pyroxene compositions: Wo1-10Fs15-64En34-85, with a mean of Wo8Fs33 (one grain of ferroaugite, Wo37Fs38, was analysed) . Plagioclase composition range is An78-94. Two grains of a silica polymorph, probably tridymite, were analysed. This meteorite is similar to LEW85441; Antarctic Meteorite Newsletter 10, #1, p. 17), and the possibility of pairing should be considered.