There is even talk about the use of egg shell powder as a calcium source for humans too. (westonaprice.org)
peppermint essential oil 3 ml eucalyptus essential oil 3 ml tea tree essential oil 1 Tablespoon walnut shell powder 1 Tablespoon fine ground pumice powder 1 teaspoon titanium dioxide cubed soap pieces, to suit (optional) (soapdelinews.com)
Add 3 grams, about one teaspoon, of egg shell or oyster shell powders, coral calcium, or other plant - based calcium sources per 1000 kcal. (darwinspet.com)