Meteorite fusion crust, 3

A fusion crust is the most characteristic feature that distinguishes a meteorite from a plain old Earth rock. If a rock does not have a fusion crust and does not contain iron-nickel metal, then there is no reason to suspect that it is a meteorite, regardless of what other meteorite-like features it may have.

Here are two views of a stone of the Mifflin (L5 chondrite) meteorite that landed in southwestern Wisconsin on April 15, 2010. This meteorite also shattered in the atmosphere, so the stone is rather blocky shaped but it still has a fusion crust and the edges are rounded. Where the fusion crust is chipped away, the interior is light-colored. This is common in freshly fallen chondritic meteorites. Thanks to Karl Aston for showing us the stone. Photo credit: Randy Korotev

These two photos were sent to me by people asking whether the rocks are meteorites. I am 100% sure “yes” for the one on the left (the fellow did not tell me where he got it) and 99% sure for the one on the right (from Morocco). Both have cracked fusion crusts, some missing fusion crust, and regmaglypts.

Two views of an unnamed meteorite from near Tindouf, Algeria. Note contraction cracks and missing portions in the fusion crust. Photo credit: Urban Zefrin

Two views of Northwest Africa 7496 (polymict eucrite). Again, the interior is lighter colored than the fusion crust. Photo credit Randy Korotev

This is a beautiful photo of a cracked fusion crust and many small regmaglypts on an unnamed meteorite (probably an ordinary chondrite) found in the Sahara Desert. Thanks to Habib for the photo.

Millbillillie is a rare monomict eucrite that fell in Australia in 1960. This is one of many stones. The fresh fusion crust on Millbillillie is redder than that seen on unweathered ordinary chondrites. I think that this is an oriented stone – it did not tumble during atmospheric entry. We are looking at the trailing side where molten rock flowed and accumulated, leading to the unusual texture. Thanks to Karl Aston for showing us the stone. Photo credit Randy Korotev

The Carancas (H4-5 chondrite) meteorite fell in Peru on September 17, 2007, making a crater 14 m in diameter, the smallest meteorite impact crater known on Earth. Highly unusual, the meteorite did not break apart until it impacted, so most of the many recovered fragments do not have fusion crusts. The total mass of the meteorite is unknown, but probably exceeds a metric ton. Thanks to Carl Esparza for the sample. Photo credit Randy Korotev

A fusion crust is the most characteristic feature that distinguishes a meteorite from a plain old Earth rock. If a rock does not have a fusion crust and does not contain iron-nickel metal, then there is no reason to suspect that it is a meteorite, regardless of what other meteorite-like features it may have.