Why this rock is probably not a meteorite:

They are meteorites.
What is it?

Coincidentally, I obtained this image in an e-mail advertisement from a dealer the same day as I received the previous photos. They are good photos (and free), so I've included them here.

Vaca Muerta is a well known meteorite. Many pieces, some up to 25 kg in mass, have been found in the Atacama desert of Chile. It's a rare and interesting type of meteorite - a mesosiderite. Mesosiderites contain silicate minerals, like chondrites, but they contain much more metal.

If you've been following all this over the past 47 photos, you might be thinking, "Well, Dr. Smartypants, how come these rocks aren't smooth and aerodynamic? Is that what a fusion crust looks like?" I think I have the answers.

These are all fragments of a large meteorite. Pieces of Vaca Muerta have been found 100 miles apart. That means that the meteoroid began to break apart as it entered the atmosphere. Some fragments may have broken off after most of the surface ablation had already occurred, which would lead to angular fragments with little of no fusion crust. Also, I suspect that large, metal-rich meteorites don't ablate to rounded stones like small stony meteorites do. The heat of ablation is conducted into the meteorite and away from the surface faster for metal than for silicates. 

If these rocks weren't so full of metal and they hadn't landed in a desert, they would be easy to overlook as meteorites. The top and maybe the bottom fragments seem to have some fusion crust, however.


Prepared by:

Randy L. Korotev

Department of Earth and Planetary Sciences
Washington University in St. Louis

Please don't contact me about the meteorite you think you’ve found until you read this and this.