Oyster shells will take ages to disintegrate.
I through them in the fire place and they are still hard.
So I gave up on them as garden soil amender.
But bones and egg shells in the fire will get soft. Soup bones will come out of my fire place snow white that you can pulverize them easily.

Do you think oyster shell for chickens could act like perlite in a pot for drainage or would there be too much mineral release?

Probably not too much mineral lease as oyster shell has low solubility.

Chicken grit (crushed granite) will have essentially no chemical effect on potting mix. It is used in bonsai potting mixes. Chicken grit is sold in several sizes. I use the "grower" size for that purpose.

Jim

My feed store has very small bags of granite for 5 or so bucks. The bigger grit 50 pounds was quartzite and had silica warnings for 6 something; I think coarse sand would be cheaper. I didn't get the price for oyster shell. Perlite is what I need but I have to order it to get the big bag. I want something to mix with my pine bark fines that isn't so expensive. I thought the oyster shell might provide some lime and be lighter.

Perlite and chicken grit are both useful ingredients in potting mixes. But I don't think they are not interchangable. Perlite is very light while chicken grit is heavy. Their water holding capacity is different, although I can't tell you in what way.

Another useful item is kitty litter, which is calcined (low fired) clay. Similar to kitty litter, but better, is Turface, which is fired at a higher heat and is more durable. Turface is used on ball fields and golf courses. It is available at garden stores.

Jim

Thanks, I have seen Turface mentioned on the container gardening forum but have never seen it in the garden centers here.

We use a few bushels of oysters annualy, and I've learned to throw the shells out under our white pine trees, or compost them together with pine needles. In a couple years shells get 'punky' and easily crumbled by hand. At that point I put them (together with pine needle leaf mold) on the garden and they get ground up by normal tilling.
This also works with mussel shels but NOT with quahoag shells.