The meteorite only strikes plots with no crystite not on the river.
Also, very often the original game would mysteriously report high crystite on all the river plots, even though they can't be mined.
Meteor strikes could hit any plot that wasn't a high crystite plot or a river plot. The maximum number of meteor strikes that could occur in any game was three times. (rarely)
According to M.U.L.E. Event Statistics on the website
http://www.smithore.com/eventstats.php, three meteor strikes were reported in 3 out of 1093 games.
The river would always report high crystite when assayed. Since you couldn't mine crystite on the river, this had no effect on the game. Actual high crystite deposits could be on the river though, with two mediums on both sides. I believe I played a game with no high crystite deposits a few times because of this. (I prefer it this way)
The store could also have a high crystite placed beneath it.