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Re: Kyanite

Madan Subramanian wrote:

> This question is for geologists or rock and soil experts: I have come 
> across a rock called Kyanite with a guy who deals in minerals.
> He tells me this contains about 54% Alumina and the rest is silica.
> He also says it does not change the pH of water and alumina will not leach
> out into water but has no idea if it is safe to use in planted aquaria.
> Any information on weather it can be safely used in planted aquaria or
> otherwise will help me a lot.

Kyanite is one of three naturally occuring minerals with the chemical formula 
Al2SiO5.  It is hard, quite abrasive and very inert.  You shouldn't have any 
trouble using it in you aquarium.  That is, if it's pure.  Kyanite would 
probably be a mined product, so you need to be sure that it isn't mixed with 
other minerals (pyrite, for instance) that are not as inert.

> This rock is a beautiful brownish red in colour and I was sold when I saw
> it.

I once kept a fist-sized piece of nearly pure kyanite in one of my tanks.  It 
was transluscent light blue.  The color didn't work too well with green 
plants.  The inevitable growth of things in the crevices and rough spots made 
it less attractive and I eventually took it out of the tank.

Roger Miller