Mick, you can get all sorts of material other than coffee in a bag of beans. When you buy, you are buying a share of a bag and all it contains. You have to be on the lookout for rocks and other matter that could potentially damage you and your hardware. There is at least one member who has had the unfortunate experience of grinder meeting rock. It does not happen very often but I have seen several small rocks and once a piece of glass in the Yemen Ismaili. Given that these are dry processes beans, it is not really surprising that they occassionally contain a few extras. Be alert!