Rust on rocks?

[Avionixx]

OK, so I bought a number of rocks yesterday that the store folk said was natural stone and probably composed of quartz. They're mostly a dark gray color with a few of them having some rust colored areas, mostly the sides. I figured the stains would just wash off, but even after hitting them with the pressure washer today, the stains still remain.

I'm assuming it's some kind of iron oxide, since it's obviously not the natural color of the rock and it does rub off if you brush it hard enough. My question is, will it be safe to use in the tank? The color doesn't leach into the water nor does it smell particularly strong. I've read that small traces of iron oxide won't do any harm, but I figured the more opinions I get, the better.

 

[Gator]

Pics will help a lot with this.

 

[Avionixx]

Ask and ye shall receive.

http://www.rreactor.com/gallery/rock1.jpg
http://www.rreactor.com/gallery/rock2.jpg
http://www.rreactor.com/gallery/rock3.jpg

Apologies about the quality, I'm pretty useless with a camera. Pictured is the surface of one of the rocks, as you can see, the water is pretty clear, but the rust-colored stains are pretty much everywhere on that particular piece.

 

[Gator]

Yikes I'd take them back and ask what the deal is. Defiantly not a rock I'd put in my tanks.

 

[CHOMPERS]

It's interesting looking. It isn't rust. It would be an even micro layer. That is some kind of mineralization. The base rock is definitely quartz. I just can't think of what would deposit on quartz to look like that. Can you tell if it is also inside the rock?

Btw, since it isn't soluble, it will be safe. Just keep up with regular water changes as a precaution.

 

[Leptar]

That looks like Granite... composed of quartz, iron ore, ect.. I would bet your PH drops... rust/oxidization is what is showing...

 

[Toddo]

Yea that does look like Granite. If so, thats iron ore for sure.

 

[Avionixx]

While I haven't broken any of the rocks in half, it looks like the brown stuff is just on the surface. While I was blasting them with the pressure washer chunks of the rock flew off and I didn't see any veins or any real penetration. Plus you can also scrub most of it off (too lazy to do it yesterday). Some people have said it could also be something called lichen?

I left them in a bucket of water for 24 hours and the PH remained the same. I realize a 24 hour period may not be enough to change the PH, but I may just give them a try after a bit of scrubbing.

 

[Leptar]

Give it 3-4 days on the ph...

If it is lichen i would look at how i would kill it before putting in your tank as it is considered a fungus.

Do the white vinegar test if you haven't already.

 

[Uppy]

Hello! If it is a real concern to you, you could do what I did with a large piece of Lace rock. I went to my local sand blast shop and had them give it a quick BLAST! Worked awesome, looked like new!