Calling all rock experts!!!

[Lulubell]

Anyone know what type of rock this is? I thought it would be safe because I got it from a lfs, but starting to have my doubts. It look as though it has rust forming on it.

 

[King Fisher]

It looks like shale rock to me but I'm no expert

 

[Lulubell]

Thanks for the reply! If it is shale is it safe for freshwater aquarium?

 

[King Fisher]

I call it shale but it's probably slate rock. Shale has clay in it which I doubt an LFS sales for aquariums. If it is slate rock then it's safe as far as I know. Slate is found in many river systems

 

[Lulubell]

Ok, thanks king fisher. I appreciate it

 

[V227]

I think you got a really pretty metamorphic rock called "Schist". KF was correct, it started out as shale, but has been super pressurized over millios of years to become Schist.
It is aquarium safe. Nice pick up.

 

[Lulubell]

Thanks v227! I will put it back in then. What I was seeing on it must have been normal aquarium crud[emoji38]

 

[Delapool]

Does look like a cooked up sedimentary rock to me as above. Pretty unlikely but you could try running a magnet near any layers where you think rust is forming imo. All I can think of would be some sort of banded iron formation to match to cause rust but pretty rare.