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.
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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.
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