I guess I still have a quarry out in the desert that I haven't covered up yet, but that's mostly due to time constraints. Another quarry I've already covered with one layer of cobble and one layer of sand to hide that there has ever been a quarry there. Although I guess it'll make a nice surprise if someone tries to dig straight down in that area
The rest of my quarries will be a few levels underground, so this shouldn't be a problem.
Also, jetpack FTW