It's like the best mineral block ever! It comes from the Manu River that flows "from the foothills of Peru's Andes to the mighty Amazon" according to the back of the package. I love, love, love Manu and will never use anything else. I also recently found out a lot of mineral blocks contain plaster of paris, which I don't think my birds should eat.
Manu contains calcium, iron, manganese, potassium, zinc (not dangerous zinc!), copper, magnesium, phosphorus, and sodium. I still offer cuttnice girlnes as well, but only from trusted sources. I just bought two huge cuttlebones from a store near my house and they are really the best kind I have ever seen. They are huge and fluffy and look great. I'm thinking of getting a 5lb box of them from The Birdsafe Store.