Millbillillie

A eucrite that fell in the Western Australian outback in 1960, famous for its glossy black fusion crust.

Key facts

Type

Achondrite (eucrite, HED group)

Fell or found

Fell (witnessed)

Year

1960 (October)

Country

Australia (Western Australia)

Mass

a few hundred kilograms in total, in many stones

Official name

Millbillillie

In October 1960, station workers in the remote Wiluna district of Western Australia saw a fireball cross the sky and break apart. At the time, nobody went looking for stones. Ten years later, in 1970, the first pieces were found on the red, stony ground of the outback. Over the following decades many more were recovered, and the meteorite became known as Millbillillie, after a sheep and cattle station in the area.

A shining crust

Millbillillie is famous for its fusion crust, the thin glassy coating that forms when a meteorite's outer surface melts during its fall through the atmosphere. On most stony meteorites, the fusion crust is dull or matt black. On Millbillillie, it is often strikingly glossy, almost like black glass or varnish, sometimes with flow lines where molten rock streamed across the surface. This appearance is typical of eucrites, because their chemistry melts into a smooth glass.

The contrast between the shiny black crust and the pale grey interior makes Millbillillie specimens especially attractive, and they are popular in collections and teaching displays around the world. Many stones are complete individuals covered all over with crust, while broken fragments reveal the pale interior speckled with darker mineral grains.

What it is

Millbillillie is a eucrite, a type of achondrite. Achondrites are stony meteorites that formed from melted rock and so lack chondrules, the tiny rounded grains found in most stony meteorites. Eucrites are basalts, made mainly of the minerals pyroxene and plagioclase feldspar, and they crystallised from lava or magma near the surface of their parent body. Millbillillie is a breccia, a rock made of broken fragments cemented together, formed by impacts on its parent body.

Eucrites belong to the HED family of meteorites, together with howardites and diogenites. They are believed to come from the asteroid Vesta, which melted early in Solar System history and formed a basaltic crust. NASA's Dawn spacecraft, which orbited Vesta in 2011 and 2012, found surface compositions matching the HED meteorites.

Desert survival

The dry climate of the Western Australian outback helps meteorites survive. Millbillillie stones lay on the ground for years before they were found, and many still have fresh-looking crusts. Many meteorites from the region have been found by people working on the land, who know its stones well. Over time, however, weathering in the desert can coat meteorites with a reddish film, and searchers must look carefully to tell them apart from ordinary rocks.

Meteorites found in Western Australia are protected by state law, and finds must be reported to the Western Australian Museum. This helps ensure that important specimens are recorded and remain available for science. Anyone searching in the outback also needs to be well prepared, with plenty of water and a safe plan, because the region is hot and remote.

Why it matters

Millbillillie is one of the most widely available eucrites, and because it was seen to fall, its stones are relatively fresh. This makes it valuable for both research and education. Scientists use it to study how basaltic rocks formed on Vesta and how they were broken up and mixed by impacts.

For teachers and students, Millbillillie is a perfect example of what a fresh meteorite looks like. Its shining fusion crust, smooth rounded surfaces and pale interior show clearly how a rock from space differs from an ordinary stone. Specimens are held by museums and collectors worldwide.

If you ever see a Millbillillie stone, notice how its crust reflects the light. That glossy skin formed in just a few seconds, as a fragment of an asteroid's volcanic crust blazed through the sky over Western Australia.

Did you know?

See more

Millbillillie in the catalogue