I'm not certain, but I'd suspect the first two are some sort of calcite... - see if you can scratch it with a nail (or other pointy steel thing). If you can, it's not quartz based, and is likely calcite.
You can also try the acid test, which tests for carbonates (acid reacts with -CO3, produces CO2), but it's not very reliable (a lot of rocks don't noticeably fizz,etc.)
Cant say for the last one, it looks like it could be limestone from the way that it's weathered, but nothing really indicative.
I'm pretty sure anubias will attach to almost anything rough/porus, given a bit of time.