Just got Lace Rock..any advice or articles?

I just bought some lace rock from LFS.

Do any of you have experience with them. The guy at the fish store said that its lava rock or something and it will help raise my pH. He told me to rinse it in regular tap water and let it dry. Looked something like the picture below.

I had some pieces with some orange stuff on it. Someone other customer told me that it will grow mold on it if i dont take that stuff off and other have told me that it could leak some toxic stuff from it. Just worried if any of the rocks have iron in them. Wouldnt they start rusting?




It was cheap though about $1.79 a pound.

 

I had a piece of that rock once,i started to cut it with a dremel.When you cut real liverock,it doesn't spark? that piece did,i threw it out.And i could only imagine how all those holes would collect junk,and pollute your tank.

 

isnt rock supposed to have holes?

 

So i shouldnt use it?

 

I have a piece and it doesn't cause any problems in my tank...