Grit for ducks. Can any sea shell do?

[Betsy88pi]

Here where I live ground-up oyster shells are hard to come by. And 5 times the average price in the states. I have been hand grinding clamshells for the ducks, although the clamshells have been baking in the sun for a few months so I guess they're sterilized. Could I boil the sea snail shells?. Their huge, the size of large clams. I'll get some extra grit for the ducks now. They free range so they probably have some grit. I´ll put a photo of the sea-snail-shell later so you guys can see if it's worthy of duck consumption.
Also, I say I don't have enough calcium is because every time I put the ground clamshells or any other source of calcium the ducks gobble it up so quickly that nothing is left after a few seconds. Also, some ducks eat soo much that others don't get any. I have been having some softshells so I don't prevent the ducks from eating it. So I guess I need more calcium.

What is the cost of oyster shells where you live?

 

[HollowOfWisps]

The composition of a snail shell is actually 95-99% calcium carbonate. My normal carrier for oyster shells has been out of stock forever so I bought a bag of oyster shells from TSC and it was riddled with small pieces of metal...so I would gladly take my chances with the boiled snail shells if I had that option right now.

 

[austroberta]

The composition of a snail shell is actually 95-99% calcium carbonate. My normal carrier for oyster shells has been out of stock forever so I bought a bag of oyster shells from TSC and it was riddled with small pieces of metal...so I would gladly take my chances with the boiled snail shells if I had that option right now.

That's really scary if you found metal in there.

 

[HollowOfWisps]

That's really scary if you found metal in there.

The sad part is there wasn't just a small piece or two, but it was completely filled with small metal pieces like bits of what looked like steel wool. I threw the whole thing away and didn't let my ducks anywhere near it. I even had my husband look at it because I thought I was seeing things and there was no way someone could manufacturer something filled with metal shards like that.

 

[KaleIAm]

The sad part is there wasn't just a small piece or two, but it was completely filled with small metal pieces like bits of what looked like steel wool. I threw the whole thing away and didn't let my ducks anywhere near it. I even had my husband look at it because I thought I was seeing things and there was no way someone could manufacturer something filled with metal shards like that.

I've heard of this before, on other threads.