Why this rock is probably not a meteorite:

1) No fusion crust. The exterior of the rock (top photo) is shiny, but it doesn't have a smooth glassy coating like a fusion crust. (The field of view in both photos is about 2 cm.)

2) The bottom photo shows a sawn face. There are many vesicles (gas bubbles). This means that the rock was once molten. Very few meteorites have vesicles because very few meteorites formed from solidification of a magma (liquid rock). Most meteorites were assembled as solids.

Notice the row of vesicles along the upper (outer) surface. The outside cooled first, forming a solid skin that prevented the bubbles from escaping, so the bubbles were trapped.

Notice also that the larger vesicles are elongated. In terrestrial volcanos, this sometimes happens when the lava flows (that's probably why the vesicles in no. 16 are elongated). In this rock, however, it is likely that the gas bubbles were simply rising vertically. Gas bubbles only rise vertically when there is gravity. There is too little gravity on asteroids, which is where most meteorites originate, to produce elongated vesicles. Even on the Moon the vesicles in vesicular basalts are round.
 
What is it?

We don't know. Upon close inspection, the grain size of the crystals is large. In basalts, if the crystals were this large we would usually see some feldspar, a light colored mineral. There are no light colored minerals in this "rock." It might be a piece of slag.

Note added later: The only mineral we could identify using Raman spectroscopy was fayalite. This is consistant with other slags that we have seen and is inconsistent with any kind of meteorite.
  



www.catchafallingstar.com
www.catchafallingstar.com


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.

e-mailkorotev@wustl.edu