About 3 years ago I acquired an enormous amount of Mineral Blocks from a friend's mother. She had a Cockatiel that passed-away at the age of 17, she was heart-broken as she'd had him his entire life, and she just wanted to get everything that had to do with him or birds out of her house. So my friend just grabbed everything she had, loaded it into her pick-up truck, and then drove to my house...My phone rang and I heard "Open your garage door up, I've got the motherload of parrot stuff inside my truck and in the bed of my truck"...So I opened up the garage and saw a huge cage and a large, metal play-stand thing (both of which I dontated to the Rescue), and then there were probably 15-20 massive, plain white, unopen bags of Higgins Cockatiel seed-mix, 25 pounds a piece. i kept one of them just as a "back-up" or "emergency" bag of seed (for the next hurricane, earthquake, mudslide,, etc. that happens in Pennsylvania, lol), the rest went to the Rescue...
But there was this large box that was filled with dozens of these plain white Mineral Blocks. They are square in shape and have the wires to attach them to the cage bars coming out of the middle of each block...I took one of them to my CAV at our next appointment just to see what he thought, and he said they are basic Mineral Blocks with no added colors, flavors, etc., just blocks of Calcium Carbonate that gives the birds Calcium and Phosphorous, and lets them keep their beaks trimmed...He said they are probably the best kind of Mineral Blocks you can give your birds because there isn't anything added to them at all, they are just pure Calcium Carbonate Mineral Blocks...So I kept them...
I won't have to buy a new Mineral Block until about the year 2035 or so...