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.
What is it?

Probably a terrestrial sedimentary rock. 


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.