Calcium carbonate toxicity I can't make heads or tails of the information on the net — although there seems to be plenty of it, it seems contradictory.

Supposedly, calcium carbonate is used in antacids—yet there are warnings about ingestion and contact with skin.

I need to handle it in pure powder form. I'm mainly concerned about skin contact, should it be avoided? (Am I getting confused between two or more forms of calcium carbonate?
Looking at the Material Safety Data Sheet (MSDS), most of the issues with it seem to stem from the physical consequences of it being in fine dry powder form. This means that if you get it on your skin, it can get into cracks and pores and easily dry out your skin to the point of cracking, and will cause irritation or worse if you get it in your eyes, for example. It's not toxic if you get it on you, though -- rubbing a lump of limestone against your skin isn't going to do anything except abrade it.

So, yes, if you're working with the powder, wear gloves. And safety glasses. And long sleeves. (See also: lab coat.)

If in doubt, follow the MSDS.