Room Six at Balclutha Primary School asks :-

What is gold used for and why are there different colours of gold?

Chris Corti, a metallurgist with the World Gold Council in London, responded.

The different colours of gold arise from alloying to make the carat golds. Basically adding red metals (i.e. copper) makes the colour redder and adding white/grey metals (i.e. all other metals) makes the colour paler and even white. The lower the caratage, the more alloying metals one can use and so the wider the range of colours possible.

Gold is very corrosion resistant, so uses of gold are everywhere besides that used for jewellery. Each year over 200 tonnes of gold is used for contacts in mobile phones and computers. 41 kg of gold was used in the space shuttle Columbia for electrical contacts, brazing alloys and fuel cell fabrication. Spacecraft are often shielded by gold-coated plastic films. The windscreens of jet aircraft have a thin, transparent, coating of gold to protect the pilots from the sun's harmful rays.

As far back as the 7th century BC the Etruscans used gold wire to hold substitute teeth in place and gold alloys are still used in dentistry today. Pure gold leaf (thin foil) is available in rolls up to 20 metres long for decorating important buildings.

Gold catalysts are a particularly exciting scientific breakthrough with huge applications potential in chemical synthesis, pollution control and the hydrogen economy (fuel cells) and gold nanotechnology has exciting applications in the medical field.

Check our website www.gold.org for more information on gold.