Re: Cure of hard stools?
Calcium carbonate will cause or increase the tendency to constipation! It's very poorly absorbed by the body unless it is oxidized by stomach acid, in which you might be deficient.
Magnesium sulphate (Epson Salts) can loosen the bowel as can Magnesium citrate.
Lecithin can also be helpful and has many beneficial effects. Combining them and eliminating calcium carbonate should get things moving.
You might try reacting the calcium carbonate with an acid in how water and maybe a hand blender and see if you can get it to react. I have some calcium carbonate and found it very difficult to get to react with acids. It should turn clear when fully reacted but I have never managed to get it to do so. Releasing the carbonate, which is alkaline from calcium carbonate is very difficult unfortunately.
Malic acid can be used, ascorbic acid is not so useful due to needing hot water and the damage it can do to vitamin c. It might require a stronger acid such as HCl but if you are deficient in that then you are out of luck. It would be better to get a more absorbable form if you really need calcium. Using bone broth soup would be a better source IMO.