Now I knew that 1 and 2 pence coins weren't actually made from copper (more like a mixture of copper and zinc) but I was gobsmacked to learn that since 1992 that hasn't been the case either.
Since then our 1 and 2 pence coins are actually made of steel with a copper plate over the top! This doesn't seem right to me, but does explain why some coins will stick to a magnet and some won't. I can't believe we didn't know this. Its also possible that they may change it so that they are copper plated aluminium. Aluminium coins? we must be in the future!
An interesting article here details it all and is of interest because in the US their 1 cent coins are made of nickel/zinc and they are facing a crisis because of the rising zinc prices. Soon the metal will be worth more as scrap than its face value! (ie more than a cent) This causes all sorts of economic problems and it may casue them to either phase out or replace the 1 cent coin with something cheaper to manufacture.
Anyway...I thought that was quite interesting...