Cheese isn't a mould. It is a dairy product, whereas mould is a fungus. Some cheeses use fungi in production, such as Roquefort and Stilton, but the majority do not. Cheese is made by processing raw milk using various enzymes; if there is fungus in there, it is added towards the end of the process.

But for a real example: diamonds and graphite (pencil "lead") are both pure carbon crystals, but one is hard and the other isn't.