My grandmother used to throw all of her coffee grounds, and egg shells around her rose bushes,
and they were beautiful. Earthworms love both coffee grounds, and egg shells.
But, instead of egg shells, since I don't eat many eggs, I use TUMS,
they're pure calcium Carbonate. I crush the 1,000 Mg tablets,
they work great, easy to work with, and smell good too.
Also, Diatomatious earth is great as a snail, and slug deterrent.
Which also has trace minerals, and calcium carbonate in it.
Snails and slugs will not cross copper either.
When I could find it back in the 1970's and 1980's,
I used copper foil stripping used for soldering stain glass window pieces together.
Worked great around the edges of wooden benches, table tops, large pot edges, etc.
I saw in an article not long ago that English gardeners are stilling use it on their greenhouse benches.