I want to buy crushed oyster shell online in the most cost effective package. I only have six laying hens, so a fifteen pound bag should last a few months at least, I think. Even though it's high in calcium, I don't want to use crushed limestone, because it's insoluable and not as readily absorbed for use by the hens' gut. I've offered both to my chickens, and they very much prefer the oyster shell. The oyster shell in their bowl is a mixture of fine powder and bits the size of peppercorns or tiny peas. They definitely prefer the bits and don't eat the powdered stuff. (FYI, always available they have a big bowl of Purina Layena Plus with added Omega. And every evening, I serve them each about a quarter cup mixture of organic scratch and Farmer's Helper Ultra Kibble.) I can't remember where I bought the oyster shell I've used thus far, and don't have the packaging anymore either. There are so many brands available online, at ebay, and at amazon.com, but some of the customer reviews are awful, and some of the photographs of the product show it to be either a fine powder or big hunks of flakes or gray colored bits. I want the milk-white bits of oyster shell. ANY RECOMMENDATIONS??????