colored slate, is it safe???

[buddy09]

I found out a local masonry supplier has different colored slate on hand and I thought about picking some up. I've used the generic grey stuff for years and I know it's fine. This guy has green, red, black and purple. It's all natural stone, but comes from different areas I guess, hence the different colorations. I did some quick research so I know it's sedimentary, metemorphic rock made up of differing material depending on location....which didn't really help me a whole lot:(...I guess the simple question would be, have you folks any knowledge or experience with the "colored" slates and do you know if they are safe for our tanks......In other words, will they leech any toxic metals or alter the ph??? Generally I use rocks I collect from the stream that borders my property since they're free, but I thought I'd try using something different to give things a new look.

[bookpage]

Your might try the vinegar test on the colored slate.

[Diana]

Some of the colors might be there because of high levels of minerals that are not good in aquariums.
Iron will often show up as rust, and looks like it.
Copper will often show up as green or teal-green or almost blue rock.

I would be very leary about using the more colorful varieties of slate in an aquarium. They might be fine... but they might not be.

If you have tests for things like copper or iron you might soak a piece of the slate in water and test it perhaps once a week for maybe a month. See if anything shows up. Test the TDS, also. If anything is coming off the rock at all the TDS ought to rise in the water.
I would start with used tank water, but also test it with tap water. There might be things in the tank water (for example if the pH is different from the tap water) that might make the minerals more soluble.

Vinegar is a weak test for rocks that might raise the alkalinity in the water. OK for soft limestone, coral, shells... but not likely to be useful for slate.

[buddy09]

Thanks bookpage, Diana. Yeah, this is annoying not knowing what is in this slate or where it came from, although perhaps if I ask enough questions from the supplier I may be able to find out something useful. I stopped by to take a look Friday and they do have some beautiful pieces, various sizes and colors. The red and green slate is particularly interesting. I know I've seen red in the LFS before, so I think that's probably ok, don't know about the rest of it. Slate being a sedimentary rock means it could have about anything in I guess and no way to really annalyze it. Yeah, I know about the vinegar test, but I don't think that will show much with slate. Have to see if I can find out the source quarry for this stuff and perhaps contact them directly. I certainly don't want to set up a nice scape in a new tank, only to find out it's not a healthy environment for the fish.

[Diana]

Slate is mined all over the world, and cut to shape and shipped all over for use in floors, countertops and many other uses. If you know the slate is coming from a local quarry you might get some answers.
You will still be stuck with doing some tests at home by putting some slate in some water and seeing what happens.

I have seen some slate, used on a porch that got wet, bleed rust within a few months of installation. I have seen what I would think of as copper stains coming off a slate roof that was who knows how old.

What kind of minerals, how much, and how water soluble are really only answerable in a test that includes the sort of water they will be used in. There might be some minerals present, but are not significantly soluble in your tank water, so the slate is safe to use. You won't know that until you try it.