Since this is not my area of expertise, I searched Google under the key words "rocks storing carbon" to get these possible sources:
https://www.google.com/search?client=safari&rls=en&q=rocks+storing+carbon&ie=UTF-8&oe=UTF-8&gws_rd=ssl
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
Besides coal and oil (fossil fuels) what type of rocks store a great deal of carbon?
4 answers
If you don't know, do not respond. Your response indicates that the post was already answered.
Fine guys, I'll just do it myself if you are so bad at finding legit answers (ten minutes later) If you happen to be doing a webquest, It's limestone. You're welcome.
FINALLY