A "certain mineral"? Colloidal silver, perhaps...?
If so...Silvermedicine.org - Colloidal Silver
I'm guessing that effects from smoking the residue hasn't been tested, but I'll pass. I'm just not a cavalier as I used to be.
I've never had a problem with the light technique though. (other than the first time, when I made few hermies instead of just one) Perhaps a longer interruption, or more lumens, or both...? I just sneak her out for a few nights, about 5-10 minutes, and sneak her back in. 3 - 23 watt CFL's.

Also...if you have the room to do so, no need to cull her so she won't pollinate everything. If you cut her back and re-veg her, (re-veg link is in my sgnature) she'll resume normal vegetative growth, and if no added stresses, no future nanners. Any nanners that were left after trimming shrivel-up and die. It's like hitting the "reset" button. Also provides boatloads of new shoots which are great for clones.