Minerals in a reef tank

Everywhere I've looked, most people say only to use standard base or live rock in your tank.. However, I have seen a few places online stating that minerals like quartz and amethyst are reef-safe, provided you remove the base of it (since that has iron in it). I was wondering if this is true. Thanks, 3reefers!

 

I'm not sure about the effects of the mineral contents of the rock, and how they may or may not effect the water quality, but if your goal is to place these rocks in there for looks, then you might be disappointed once the Coraline algae takes over and covers those pretty rocks. :

At least in my tank, the coralline covers everything - the rocks, snails, hermit crab shells and the glass if I don't stay on top of it.

 

Adding crystals to saltwater creates free silicates in many cases that fuels certain nusience algae blooms.

 

+1 to both.

Land-mined rocks also lack the porosity of reef rocks, dramatically reducing their bio-filter capacity.

 

I guess I won't be placing them in my tank! I wanted them in there for looks, if they wouldn't damage my system.. But I had forgotten that coralline would grow on it. So, two negatives.

Thanks for the replies!