Salem

can the lime terrain deplete or become unable to extract boulders?

Well you can only dig slopes to a certain depth before they become too steep. But AFAIK if you keep digging out the surrounding dirt you should be able to keep digging out lime indefinitely.

On a related note, can you "re-stock" a lime deposit by dropping dirt on it to push the ground level back up? Or does that turn the Lime into dirt? This also applies to clay deposits.

no, it wont let you place dirt on these resources, clicking causes your guy to walk there but do nothing,.

Thats actually not true, if you have the right set up you can put dirt on the surrounding tiles and you will indeed "restock" the lime quarry.

Just note that this IS a bug and will be fixed at some point.