Meteorite Fusion Crust, 3

A fusion crust is the most characteristic feature that distinguishes a meteorite from from a plain old Earth rock.

If a rock does not have a fusion crust, 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’m 100% sure “yes” for the one on the left (the fellow didn’t 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 cracks and missing portions in the fusion crust. Photo credit: Urban Zefrin

Two views of Northwest Africa 7496 (polymict eucrite). This meteorite is very fresh; the fusion crust is still shiny. On the left, clasts are evident as protrusions. (I think this is a bit unusual.) Click on image for enlargement. Again, the interior is lighter colored than the fusion crust. Click on image for enlargement. More photos here. 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 chondrite. Thanks to Karl Aston for showing us the stone. Photo credit Randy Korotev

Rough fusion crust on small fragments (millimeter ticks on left) of Carancas (H4-5), which fell in Peru on September 17, 2007. Thanks to Carl Esparza for the sample.

A fusion crust is the most characteristic feature that distinguishes a meteorite from from a plain old Earth rock.

If a rock does not have a fusion crust, then there is no reason to suspect that it is a meteorite, regardless of what other meteorite-like features it may have.