Sandstone?

One of my brothers just dropped off a half a 5 gallon bucket of free range sandstone rocks. None very large, some are pretty interesting as far as shape goes. One thing I did notice is that several of them have iron stains. Would the rock itself or the presence of iron stains be any cause for concern?

 

I think it’s always good to play it safe when introducing metal ores into your aquarium by just simply not doing it lol. When it comes to sandstone it will cause your ph to raise so if you have a low ph and want to raise it this is a good option .

 

First, what kind of sandstone is it? There are different types of sandstone and the different types have different mineral compositions and thus element concentrations. A picture would be nice. If it is what I think it is, then it is probably a quartz sandstone.
For me, it would depend on how much iron staining there is. If it's just a few bands of iron, you're probably fine. People always recommend lava rocks (like scoria) or basaltic rocks. These rocks can have up to 8% iron while a quartz sandstone has at most about 3% (probably less than 1%). Bacteria is not my area of knowledge but you need to sterilize your rock prior to use in the tank.

Sources:

 

I'll get you some pictures tomorrow. It's just a red Texas sandstone from south of Fort Worth.

 

I'll get you some pictures tomorrow. It's just a red Texas sandstone from south of Fort Worth.

The red coloring is from iron cement. I'm not finding numbers for the concentrations of those types but they will be higher than the usual sandstone. If it's red sandstone, it might be okay, but I'd probably err on the side of caution and not put it in.

 

The red coloring is from iron cement. I'm not finding numbers for the concentrations of those types but they will be higher than the usual sandstone. If it's red sandstone, it might be okay, but I'd probably err on the side of caution and not put it in.

I wasn't able to get any good pictures. A person might be surprised to find out how difficult it can be to take a good picture of something as common as a rock, I know I was. Sheesh. Anyway, I talked to my brother and he said that they came off of his property and were definitely sandstone. He's not a geologist but is a civil engineer who's spent 35 years moving dirt out of the way to build roads and knows at least a little bit about what he's looking at. I was doing a little more google-fu and just typed in "sandstone in aquariums" and was led back here to FL - namely this thread.

Why can't sandstone be used in the aquarium?

I'm going to follow the advice proffered there and see what, if anything, comes of some simple soaking. It sounds like it should not be an issue and it shouldn't take long to find out if there might be a problem. At this point my gut says it'll be fine but I'll do my due diligence.

Thanks for your input, it is appreciated.

 

So after letting some of this stuff soak for a day I got a chance to clean some up and look at more closely. I'm beginning to think that it's not sandstone, at least most of it isn't.
It may be mudstone. I mean, it looks like mud. I've seen sandstone with a lot of silica and it would almost glitter and even the stuff that didn't have that glittery look, it FELT like sand. You could rub it and just feel the grit. One piece he gave me is kind of like that but most of it almost has a moonlike texture to it with pockets/craters and what looks like the effects of erosion. Also, this doesn't have the layers the same way that any sandstone that I'm familiar with does. It does have some stratification but not much.

I did give it all the vinegar test though and none of it shows any signs of calcium carbonate, so that's good.

I'll give it a little longer soak and check the pH just to be on the safe side.

 

Here's a picture of some of it. Almost looks like something you'd find in a mudpot at Yosemite. You might also be able to make out some of the orange-y coloration/splotches from the iron leaching.