This event would be uncommon like the storm. Unlike the storm, it would be boradcasted globally.

A larger meteor falls from the sky and has to be mined. It rewards a lot of gems to the first players to find and mine it.

You could either have the event happen more often with the meteor having less health to reward the first lucky few; or you could have the event happen less often with the meteor having more health to buy time for more players to arrive and be rewarded. (I would recommend the prior, as the latter may just end up giving even more gems to the first powerful players to arrive while other players struggle to locate it, receive nothing and have to wait a longer period for the next one.)