While researching Western Australian meteorites, a problem arose in the mind of the writer. Many meteorites have been found in Western Australia, a product of its arid climate which preserves the stone from oxidation longer. Also the remote countryside means they have lain undisturbed until meteorite collecting became popular. Yet specimens are seen labelled for only a few well known locations. Hundreds of stones for example have been found on the remote and vast Nullabor Plain, scattered as individual or within small groups from separate falls. There is a danger all this material simply gets lumped as the Mundrabilla meteorite. Whether this concerns meteorite collectors is another matter.

There is a similar concern between the Wiluna meteorite shower and Millbillillie. Both are separate falls on different dates, in the same general vicinity. It is believed hundreds of stones were collected by individuals after the Wiluna meteorite shower, so the question is, are these stones being sold correctly?

On the 2nd September 1967, a large meteorite shower fell due east of Wiluna in an elliptical area 5 x 3 kilometres wide. The meteorites came from the south-east. It is estimated 500 to 1000 stones hit the ground. The Western Australian Museum has 480 stones and many fragments, some are also in the School of Mines Kalgoorlie, and many more in private hands.
The largest stone in the museum is 14kg and smallest 2.2gr.Specific gravity is 3.69.

The stones have a black fusion crust with light grey finely mottled interior. Some areas of the surface are pitted, while some are smooth with irregular pits. Some show an unusual characteristic of having two types of crust on the same stone; thin brown striated crust and thick black warty crust. The reference states this is from two distinct fragmentation events.

The interior of some specimens show a brecciated pattern traversed by veinlets of dark glass. Another unusual aspect for a chondrite is some show relatively prominent metal nodules up to 2.5cm in length projecting through the crust. While many of these specimens were picked up shortly after the fall, some were stored outdoors and therefore may show oxidation along the cracks.

The interior shows small chondrules less than 1mm, with hazy outlines, enveloped by a corona of opaque minerals. Olivine and bronzite are abundant with other silicates very minor. The chondrules are olivine phenocrysts and fan types, with olivine and orthopyroxene needles making the fan shaped aggregates.

Scattered skeletal specks of kamacite aggregate with sub-ordinate troilte at a 4:1 ratio. Larger nodules of these display taenite and plessite within a large expanse of kamacite. Dark opaque magnetite dusted glass fills veinlets of the breccia.

The reference states the meteorite belongs to the Van Schmus and Woods class 4 of the olivine-bronzite chondrules (Urey and Craig H group, in the Rose-Tschermak-Brezia classification). Alternatively it is an intermediate veined brecciated crystalline chondrite.

Coordinates as per Meteoritical Bulletin Database.

Other Regions, Features and Areas containing this locality

References