Why this rock is probably not a meteorite:
This is the sawn face of a rock that someone sent us because they
suspected that it was a lunar meteorite.
There is a large crystalline mineral grain at the center and above
the center. It's colorless with black inclusions (probably some
oxide mineral). It's rare to find such large mineral grains in any
kind of meteorite. If the rock were lunar, this grain would have to
be plagioclase. The grain looks like quartz, however, (translucent,
colorless). Quartz doesn't occur in meteorites,
but it is common in terrestrial rocks and inclusions like this are
common in terrestrial quartz. The dark inclusions are oriented
vertically, yet there is some hint of linear fractures running almost
horizontally. We are unaware of any meteorite that shows preferred
orientations of inclusions or fractures in any mineral grains.
Brecciation (breaking apart and gluing back together) by the impacts
of meteorites on asteroids and the Moon tend to erase preferred orientations.
Bottom line: There's nothing about the rock that looks lunar
and there are several aspects that look characteristically terrestrial.
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What is it?
Probably a terrestrial sedimentary rock.
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