Gina McHerron, of Kaikoura Primary School, asks :-
What metals are in our coins?
Gordon Dry, the manager of the Policy and Supply Currency Department at the Reserve Bank of New Zealand, responded.
Our silver coloured coins are made from a mixture of two metals, copper and nickel. When mixed together, three quarters copper and one quarter nickel, the mixture is known as cupro-nickel. Our gold coloured coins are made from a mixture called aluminium bronze which is mainly copper (92 per cent) with some aluminium (6 per cent) and a little bit of nickel (2 per cent).
Both of these mixtures of metals are used a lot to make coins throughout the world. They both keep their shine for a long time, they are soft enough to stamp a good 'heads' and 'tails' on them, yet they are hard enough to last a long time in shop tills and in peoples pockets without the design wearing off.
Many years ago, gold coloured coins were made from real gold and silver coloured coins from real silver. As time went by and the buying power of coins went down and as bank notes were made and used, gold and silver became too dear to use for coins that were not worth very much.
The making of coins is very interesting. First, the blank pieces of metal are cut out of large sheets of metal, the blank pieces are then stamped with steel punches that have the `heads' and the 'tails' engraved on them. The stamping is done on both sides of each piece of metal at the same time by huge machines which apply enormous forces of about 100 tonnes.
The Reserve Bank has lots of coins made each year. This year (1999) we are having 25 million 5 cent coins made and 5 million $2 coins made. The coins are being made overseas.