Corundum is a name for aluminum oxide in mineral form.  It is hard, relatively inert, naturally transparent and clear.  When it naturally appears with impurities, it can be colored and is called ruby or sapphire. It's also called alumina.  Because of it's hardness and ready availability, it's a principle component in sand-paper, which is mainly some hard grit (like corundum) glued to a paper backing.  You could view the millstone as mainly some hard grit (like corundum) mixed into a ceramic clay and kiln-fired into a millstone.

As far as safety goes, all the Material Safety Data Sheets I've been able to scrounge up on alumina or corundum basically state that it's categorized as a "nuisance dust", and you don't really want to be breathing it or rubbing powdered alumina into your skin or such.  There's no real danger to eating it in small quantities.

I have a WhisperMill; I think Nutrimill might have bought them out. I've had mine for over 15 years. I really don't think it matters what you get as long as it grinds grain. :)

I tend to grind about 5 lbs of whole wheat flour, a bag or two of popcorn, and 10 cups of rye flour at a time (stored separately of course!). It's quick, and then I stick the flours in the fridge. I rarely use the mill...it does its job, and then it goes away. I guess my advice would be, don't worry too much about what you get, just get one and enjoy! 

HTH,

Ria

Same as Rea, have had my whisper mill for over 15 years, have run several hundred pounds thru over the years making 10lbs of dough at a time for 5 loaves, max that fits in myoven. 

Stones break down on a microscopic level and if the aluminum pots of the fifty's were linked to alzheimers, why take a chance on aluminum oxide, as inert as it may be?

Very happy with flour, usually 5lbs at a time that is done in a few minutes, moreover, the temp doesn't rise much at all, thus keeping the nutrients intact.  And flour is very fine, which I prefer, can be made courser. 

Nothing, I mean nothing tastes better than a whole grain loaf made from fresh ground flour, expecially when using rye in addition to whole wheat.  Store bought just doesn't cut it, even the high end flours like KS will taste stale by comparisson.  You'll never go back...  Good luck!!

Thanks for the input so far. I desperately want to believe blaisepascal and not worry about it. I had become quite attached to the idea of the Wolfgang/Komo. It looks so easy and compact. I was sure I'd finally join all of you in experiencing a delicious loaf unlike anything I've ever tasted before! Everyone's descriptions make me salivate with envy.

But I'm hesitant to put this man-made material in the "innocent until proven guilty" category. With further searches I found a site that talks of the production of making alumina based ceramics. I don't know if this is the same thing as ceramic corundum, but the additives look scary toxic and additionally bad for the environment. Of course I don't know the relative environmental impact of making steel burrs or plastic housing of the Nutrimill. Also the Schnitzer site talks about "new grinding edges" being constantly exposed with their corundum stones (they mention this as a positive). Despite assurances that it is trace amounts that end up in the flour and completely safe, I'm not sure I want to be eating the "old grinding edge". I'll have to ponder if I will turn a blind eye to it. Any other input or opinions are appreciated.

http://cnx.org/content/m22376/latest/
http://www.grainmills.com.au/webcontent60.htm

Forgot to mention one thing in my post above: When using my Whisper Mill, I usually add a fair amount of flax seeds to the whole grain and grind them together, gives a nice subtle flavor, plus very healty addition.  The Whisper Mill can easily handle this, whereas stone mills would likely not as the oil may clog the stones...  Can't argue about how pretty the German Mill is with its wood case, but I'm all for functionality...  thanks and good luck no matter what you pick, fresh ground rules!