How to make large potassium-based crystals?

[iansmith]

I am looking for an easy way to make a large potassium-based crystal.

 

I'm not particular about the exact chemical used as long as it's non-toxic and not too expensive. Potassium chloride was my first thought since you can buy it as a salt substitute.

 

I was looking for something like this... http://www.mindat.org/photo-22231.html

 

The bigger the crystal the better. A group of smaller ones works too, as long as they are are all fused together.

 

I have never played around with growing crystals before so I have no idea how to pick the 'best' source material, or if it even matters.

 

Thanks!