Reef Safe Rocks from Quarry?

[Paradox009]

Hello, Im looking to find flat rocks to create large shelves in a new aquarium. At my local landscaping supply, I faound numerous large flat rocks that would be the perfect shape, but I want to be sure they are reef safe. Does anyone know what type of slate or other rock is safe? Some had some orange hues that I suspect may be oxidation. Does anyone knowledgeable about different rocks avalable that would be reef safe?

Thanks!

- I was thinking of making some agrocrete ones, but was turned off byt the long cure times. I do not need the rocks to be porous, are there other methods for making your own custom rocks that does not require months of curing?

[minimalist]

I wouldn't use anything foreign. You never know what it will leach into the water.

[HBtank]

I would not use slate.

[Fraggle Rock2]

You could always just chisel/break/sand etc some reef base rock.