Shale?

Any thoughts or comments on using shale for hardscaping? In particular for a planted aquarium.
I have a small sample i will do the vinegar test on later, will post results.

ian did a post about the vinegar test a while back that was most informative.I'll try and dig it out.It's not really very good by all accounts.

Gavin wrote:

ian did a post about the vinegar test a while back that was most informative.I'll try and dig it out.It's not really very good by all accounts.

Do you mean Ian's post was not very good by all accounts?

Now, I'm not a geochemist so I won't go into the chemistry of the rock too much.

Shale..???..... it is quite a varied 'rock' really that could contain many things depending on source and how it was formed in the first place.

So, on there being so many unknowns it is difficult to say 'yes' or 'no' to an unknown piece of shale.

The principle composition of shale itself is not particularly harmful, BUT.....it may have formed in what are called 'reducing' environments OR it may have various impurities that make it toxic to fish.

Certainly any shale that is black is something to avoid as the black colouration may be due to a reduced form of carbon (or un-oxidised organic materials) OR (and very likely) it contains iron sulphide.

Iron sulphide is a hazard in a tank:
what can happen is that some bacteria can develop and turn it into hydrogen sulphide (highly toxic), then as you produce nitrates the combination of iron sulphide and hydrogen sulphide will act to convert a large amount of the nitrate into ammonia (not good).

Apart from iron sulphide, black shale is also likely to contain noticeable amounts of heavy metals (eg Zinc).

But all of that does not mean all shales are potentially toxic.

The Vinegar Test..???.... I think I have said that I bemused as to how come the 'vinegar test' is still used as a test of 'safeness'. I probably need a lesson in chemistry to show me the error of my thoughts.

All the vinegar test will tell is if the rock contains carbonates (releases carbon dioxide gas) or certain metals such as metallic iron or zinc possibly.

The bubbles formed do not tell you the rock is unsafe.....there is nothing wrong with putting calcium carbonate in a malawi tank say.....but more importantly, no bubbles means one thing: no bubbles !! and that is about it.

No bubbles is absolutely no indication of safeness when using the vinegar test.

There is also another item that should be noted here especially with shales....... adding acids to rocks can be highly dangerous to you if you are not sure about what gases can be produced.
If you added, say, some dilute hydrochloric acid to black shale in your front room then you could produce enough hydrogen sulphide to kill you.

Anyway, soz about the longish post.
The overall choice depends on how confident you are about using it....as I said, no all shales are potentially dangerous.

Ian

Thanks for your very informative input Ian. The place i was looking at the shale is a large area, and on further inspection i noticed quite a few different shades of the stone, which coincides with your information on how it was formed. I have a small piece i took to test (private property with owners permission) but have no vinegar in the larder!

Ians info, and my gut feeling means I think ill give it a miss, just don't want to take any chances. Was thinking again today about wood as an alternative for my hardscaping, but then one gets into the "My water is yellow and my wood is floating! scenario! (

I don't want to sound negative, but there are a few things to consider.

It would be nice to have a safe supply of certain rocks...especially ones that could even be shaped somewhat.

Maybe if you knew a geologist, then they may be able to give an indication of what is likely to be in the particular batch of shale.
If it is obviously formed from, say, a deep anaerobic pool and you see much black then the chances are it should be avoided unless you can get a better test than the vinegar test.

But the basic stuff in shale is quite safe.

A Daphnia culture is sometimes a good way to test for some poisons in water. They don't tend to give ppm readings though....they don't read the labels on the test bottles

ian

Well, Got vinegar. The 2 samples i have rock didn't fizzle. On further inspection, the 2 samples are quite different.

One is more like limestone (first pic), i flung it round the back yard and wouldn't break, it is a grey color, and i noticed the sparkle of metallic speck in it. I can see the formation of it is in layers.




The other stone from the same place is closer to sandstone.If i scrape it with my nail I can saw off dust, if I was easily able to crack it to pieces with a hammer.



My gut instinct is still telling me "NO, Jason, Dont do it!" the first has metallic specks, and the second is too soft.

Have to tell you, that is not Slate or Shale, not even close, the first one is Granite and the second looks like Sandstone.

Kev.

stretnik wrote:

Have to tell you, that is not Slate or Shale, not even close, the first one is Granite and the second looks like Sandstone.

Kev.

I can't see the second one too clearly on my laptop, but I agree with Stretnik on these 2 pieces of rock.

The 'metallic specks' maybe the normal lustre of quartz in granite or simply mica in granites.

Well I suppose if its granite, that's not so bad, from what i read its neutral.

Being thinking more about my hardscape, and will use a small amount of rock to create natural border between the aquasoil in the planted areas and pebbels in the foreground of the tank that will be unplanted. Ill go bogwood for the main decor, found some great chunks at my local maxizoo.