Sample No.: BTNA78004

Location: Bates Nunatak

Field No.: 324

Weight (gms): 1079.0

Meteorite Type: LL6 Chondrite

Physical Description:

One surface of this sample is a fracture surface. The remaining surfaces of the sample are covered with thin (0.5 mm), dull black fusion crust. Regmaglypts are present on the N and S surfaces. Macroscopically, the sample appears to be composed of angular, light colored clasts, surrounded by greenish-brown to gray interstitial material. The clasts comprise approximately 70% of the surface area and have a wide range in size; some are as much as 2.0 cm in diameter. Chondrules are apparent on the surfaces exposed during cleaving. Dimensions: 12 x 7 x 7 cm.

Petrographic Description: Brian Mason

The section shows a granular aggregate consisting mainly of olivine and pyroxene (average grain size 0.1-0.2 mm), with minor amounts of plagioclase, nickel-iron, and troilite, and accessory chromite. Chondritic structure is barely visible in a few places, and the chondrules are somewhat fragmented. Many of the silicate grains show undulose extinction. The meteorite has a brecciated structure, and the breccia fragments are outlined by an anastomosing network of black glassy veinlets which contain numerous minute troilite globules. A small amount of limonite staining is present around some of the nickel-iron grains. Microprobe analyses show olivine (Fa30) and orthopyroxene (Fs24) of essentially uniform composition; plagioclase is somewhat variable in composition, An13-An22, average An19s. The black glass is quite variable in composition, as follows (range and average, in weight percent): SiO2 31.5-49.9, 40.4; Al2O3 0-6.3, 2.8; FeO 17.5-40.9 23.9; MgO 16.7-31.3, 27.3; CaO 0-3.3, 1.6; Na2O 0-2.4, 1.1; TiO2 0-0.15, 0.09; MnO 0.3-0.5, 0.4. The meteorite is classed as an LL6 chondrite; it shows to a high degree the brecciation characteristic of many LL chondrites.