Why this rock is probably not a meteorite:
1) This is one of several large rocks found in a ravine in Mexico.
A ravine full of rocks is among the least likely places to find a
meteorite. Meteorites are usually found in places where terrestrial
rocks are scarce. Meteorites undoubtedly occur in ravines, it's just
that they're hard to recognize among a pile of terrestrial rocks.
Also, meteorites don't survive long in wet environments.
2) It doesn't have a fusion crust. It
doesn't have the aerodynamic shape of a meteorite.
3) It's got veins or ridges that stick out. If this rock came through
the atmosphere from space, the ridges would have been the first things
to ablate away.
4) There's a big linear or planar feature running right through the
center, top to bottom. Many terrestrial sedimentary rocks have planes
because they formed from material settling to the bottom of a sea
or ocean. Meteorites don't have linear or planar features because
they come from asteroids with no seas and not much gravity.
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What is it?
Probably a terrestrial sedimentary rock. Speculation: The sedimentary
formation (carbonate?) was fractured and then quartz was deposited
from solution in the fractures. The resulting veins are harder and
stand out in positive relief because quartz is harder than carbonates.
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