I think it might be different from state to state and/or country to country.  Please specify a general area of residence.

Starts with any sort of rock, then the following processes occur.

Weathering
Deposition
Erosion
Lithification
Compaction

In that order, specifically.

www.rocksandminerals4u.com

Yeah, bats are a carrier for rabies.  Animal control is a good idea, if you have it in your area.  You could potentially open the garage and let it fly out as well... There is no reason to be afraid of bats.  They don't attack humans.