All that glisters...

In the latest of our features by lecturers at the University of Huddersfield, head of chemical and biological sciences, Dr Robert Jewsbury, looks at man’s fascination with gold

With the price of gold now over $1000 per ounce, the rush is on both to buy new gold jewellery and to sell old gold articles for recycling.

The average rise in sterling has been nearly 20 per cent per year over the last five years – much better than the interest rate in the bank, but that does not mean that it will continue.

What is special about gold and why is the price rising?

The majority of the known elements are metals, but gold is one of the few that may be found as the metal itself rather than as an ore and has been known for many thousands of years.

Most metals are silver in colour, because they reflect all the colours equally.

Gold and copper are unusual in being coloured. Copper has a reddish colour when freshly cut, but unlike gold does slowly tarnish in air.

Gold can be found in its natural form, it has a unique appearance, does not tarnish and can be easily worked into shapes.

It is also rare and so it is not surprising that it has been used since earliest recorded times in jewellery and for coins.

For practical use in jewellery, pure gold is too soft and so it is usually mixed (or alloyed) with other metals such as copper and silver.

As these are much less valuable, it is important that the purity of the gold is known and so no jewellery can be sold in this country as gold without the purity being marked by an Assay Office.

The earliest of these was Goldsmiths Hall in London, which is why we refer to this as hallmarking.

Pure gold is 24 carat and lower carats refer to the proportion of gold.

Thus 9 carat is 9/24th gold or 37.5 per cent.

The hallmark must include the manufacturer’s mark, the purity and the assay office and may optionally include the date of assay.

The proportions of copper and silver will affect the colour.

Increasing the copper makes the gold more pink and the more silver the lighter the alloy appears.

The Assay Offices usually determine the purity and composition by a non-invasive technique using X-rays so no damage is done to the jewellery. In this country, white gold is becoming increasingly popular.

This can be best achieved by alloying with nickel, silver and zinc, but because nickel might be slowly released from the jewellery and can cause an allergic response in some people, the use of nickel is restricted in Europe and palladium, again with silver and zinc, is often used.

With palladium, the colour is often not as silvery as required, so the item is rhodium plated.

This can still be hallmarked as gold and you may not be told about the plating.

This will wear off in time, so it is worth asking if your white gold has been plated.

The industrial uses of gold, particularly in electronics, depend upon its good electrical conductivity and absence of corrosion but these make up only 10 per cent of the usage with around 65 per cent going into jewellery and 25 per cent as bars for stocks or investment.

The source of gold is the rocks in the earth’s crust.

The concentration is not high overall but is localised to certain regions.

Interestingly, it is estimated that only 2 per cent of the earth’s gold is in the crust the majority is in the core but that is inaccessible for the foreseeable future.

Transmuting base metals into gold was the aim of alchemists for many years.

While it is possible to convert other elements into gold using nuclear reactions — that is how the gold was formed in the first place — there is no suitable process for doing this on a large scale.

There are gold salts in seawater, along with those of many other metals, but the concentration is very low – only one gramme for every 100 million tonnes of water. It used to be thought that it was larger and there has been interest over the years in extraction.

In the 19th century there was an elaborate fraud.

Two Americans invented a device that when lowered into the sea accumulated particles of gold overnight.

They founded the Electrolytic Marine Salts Company and investment flowed in when they appeared to be obtaining gold from the seawater. Eventually the two friends who set it up disappeared abroad with much of the money and it emerged than one of them was a trained diver.

Investing now in gold is not as foolhardy as investing in the Electrolytic Marine Salts Company, but in the short term the price could just as easily go down as up so buy jewellery because you like it, not for investment.