Some Black Shale Not Inert

[mooman]

Some Black Slate Not Inert

Hey all, just thought I'd post a resolution to the delema I've been experiencing. I've always heard slate is inert so have used it extensively in my apisto tanks. I have been trying to lower the ph in these tanks unsuccesfully for months. Recently a fellow hobbiest mentioned that local slate contains alot of calcium. To test this assertion, I filled two glasses with RO water (ph=6.6) and added some slate chips to one. After 25 hours the ph of the water containing the slate had risen to 7.0, the glass with no slate had not changed. Mystery solved. It only seems to buffer the water up to about 7.2 however, so it still makes a good rock for community tanks.

 

[Roan Art]

Oooooooooooo, has he ever tested soapstones, perferably steatite? I have three huge black pearl soapstone rocks in my 36 gal (one is 29#) and the pH drops from 7.8 to 7.4 after water changes. Doing an investigation on the drop atm.

Steatite is a little harder than soapstone and softer than shale. I got their forumla off the mindat.org database: Mg3 Si4 O10 (OH)2

Mg=magnesum, Si=Silicon, O=Oxygen, H=Hydrogen

OH? I could ask hubby, but he just walked out the door. Someone else can break this down and does anyone know what the effects these have on water properties?

Roan

 

[daveedka]

Err Um Shale is a sedimentary rock, therefore it would not typically be inert.
Slate is metamorphic and is usually inert. The two are often confused with each other.

In most cases shale will leach compounds as you have found. additionally most shale will turn to mud after extended exposure to water. Depending on the area, makeup, and density a given piece of shale. the melting effect will work at different speeds, but it is always present.

Soapstone and similar rocks will typically melt. The Mg will definately increase hardness, I'm not sure what exact effect the silicone will have if any. But in any case it will have an effect on water chemistry.

Dave

 

[chefkeith]

I'd do a GH test with RO water and the shale instead of a ph test. If the GH goes up, then you know that magnesium or calcium ions are be added to the water. The pH of RO water is not stable.

 

[mooman]

You're right dave, I did indeed mean slate, and not shale (don't know where my head is at). It's the stuff you gave me at 1st swap meet. Thanks again, by the way. It would have cost me a fortune to buy it retail, and it works great in my display tank. I guess I just can't use it with ultra soft water fish.

ps any way to fix the actual thread title to slate instead of shale?

 

[daveedka]

It's the stuff you gave me at 1st swap meet. Thanks again, by the way. It would have cost me a fortune to buy it retail, and it works great in my display tank. I guess I just can't use it with ultra soft water fish.

Interesting, Now I'm going to have to test some as well. The stuff I brought in that day was all from a pretty good sized slate producer in Ky and should be good inert rock. It was a little crumbly for slate which now makes me wonder since you are seeing some leaching. Of course since I didn't test it all things are possible. I would do a GH test if possible. The PH of Ro water as said is pretty unstable. I have quite a bit of that slate in my tanks, but then again, I am trying desperately to increase hardness so I would not notice a small increasein Gh if it came from the shale.
Dave