The Old Troyes Gold Trick
Friday, September 18th, 2009One of the old routes for a traveller from England through France and on to Italy passed through the French city of Troyes, situated between Reims and Dijon (nowadays at the junction of the A5 autoroute (from Paris) and the A26 autoroute (from Calais) – the A26 is still called the Promenade des Anglais and to this day sees a steady procession of vehicles bearing UK plates heading to & from the Channel). Many centuries ago the only way for travellers to pay for goods & services was with gold & silver coins. Troyes gave its name to the troy ounces in which gold is still traded today.
However there was no standardised system of weights & measures in the Middle Ages and merchants who travelled across Europe had to contend with each different city they arrived in having its own definition of how much an ounce or pound weighed. There were the pound of Toulouse, pound of Cologne, the Wool Pound, Mercantile Pound and London Pounds. Pity the poor traveller who was handed an ounce of gold in one city which weighed less than an ounce of gold when he got to Troyes. Never mind the fact that there are 12 Troyes ounces in a Troyes Pound but we all know today that there are 16 ounces to the pound we use in cooking, etc (strictly called the Avoirdupois ounce). And we haven’t even touched upon the Kings’ habit of debasing their currencies by having coins minted of alloys which contained progressively less and less than 100% pure gold – there were many ways in which the merchants of the Middle Ages could be hoodwinked!
Silver is also traded in troy ounces. Sterling Silver is an alloy which contains 92.5% pure silver (the rest is usually copper). Centuries ago the Spanish minted silver and gold coins. The Spanish silver coins were called Reales and a 1 Reale coin contained 0.125 ounces of silver. Thus the 8 Reale coin contained one ounce of silver - the 8 Reale coins were the Pirates’ fabled Pieces of Eight.
Gold is once again in the headlines now it is trading above $1,000 per troy ounce. The Comex gold futures contract (symbol GC) is based on 100 troy ounces of gold which means if you own one contract at expiry you will receive 3 one-kilogram gold bars of at least 99.5% purity. This is not quite 100 troy ounces of pure gold but it makes the GC futures market function better. Being short-changed in gold is something people have got used to over the centuries!
In terms of grams, a Troy ounce = 31.1034768 grams whereas an Avoirdupois ounce = 28.349523135 grams. Curiously a Sterling Silver coin weighing exactly one Troy ounce contains nearly one Avoirdupois ounce of pure silver, just as today’s Krugerrands (made of 22 carat gold alloy) actually weigh more than a Troy ounce so as to contain exactly one Troy ounce of pure gold.
So don’t fall for the age-old trick of thinking that your 9-carat rose gold bracelet which your kitchen scales tell you weighs one ounce is worth anywhere near one thousand dollars. In fact as rose gold is usually gold alloyed with copper and 9-carat gold only contains 37.5% gold, your rose gold bracelet would be more accurately be described as a copper bracelet. All that glitters is not gold – as the merchants may well have said in the taverns of Troyes after a good day’s trading in the Middle Ages!
