Hey Woodsman, I can't help you with the aluminum salts in crystal deodorants but I found a natural deodorant that really works for me. I do tend to sweat quite a bit and most natural options don't work as they either don't last or give me a rash.
Sodium bicarbonate on its own never worked for me because it didn't last long enough. But I accidentally came across
this brand and it does the job very well. The list of ingredients has lots of different oils and fats but the deodorant isn't greasy at all. The active ingredient is bicarbonate of soda and arrowroot powder removes the greasiness.
This brand s very pricey so I make my own version of it where I mix bicarbonate of soda, arrowroot powder, fat or oil (I use beef dripping but I guess coconut oil would do the job too) and lemon essential oil and blend it into a paste. It seems to work even better than the 'original'!
You could make a bit more of it and put it into a deodorant stick as it feels almost the same if you leave it for a couple of hours.
Chu suggested trying soda bicarbonate with lemon juice - maybe that's why my combo with lemon oil drops works so well actually.
Those crystal deodorants worked for me too but I didn't want to risk the science behind their safety being as good as the science that proves fluoride is good for our teeth so I discontinued them. As different things work for different people, since we both were successful with crystal deodorants maybe the above mixture will work for you too?