About Jewellery » What Makes Precious Metals Precious?
Precious indeed. Platinum, gold and silver are among the world's most precious, or noble, metals. Their rarity and the difficulty in mining all of them are big factors in their price. Gold makes up only 3.5 parts per billion of the earth's crust, platinum is 45 parts per billion (but more laborious to extract and refine) and silver about 73 parts per billion. Approximately two and a half to three tons of ore are mined to extract one ounce of gold.
But these noble metals are also prized for their beauty, their workability and their durability. Their physical allure comes from their attractive attributes of colour, lustre, and heft. Their colours are rich, and as I describe in "Karats or Carats?", can be enhanced with the addition of alloys. The lustre, or reflected light, of all of them is very high. Pure polished silver has greater reflected light than any other metal on earth, reflecting more than 90 percent of visible light back to the eye. The heft (or weight for size ratio) of all of these metals gives each of them a tactile beauty. Platinum is the heaviest of the three: a cube of pure platinum measuring about 15 cm (6 inches) on each side weighs over 76 kgs (169 pounds) - the weight of an average man!
But beauty is as beauty does. Not only are they pleasing to the eye but they are easy to the hands. They are malleable, that is they can be stretched in all directions without breaking and they are ductile, that is they will hold the shapes they are formed into and not bounce back. An ounce of pure gold, about the size of a small cracker, can be rolled into a 9.32 metre (1002 foot) sheet that is 0.000127 mm (5-millionths of an inch) thick. And that same ounce of gold can be drawn out into a wire 80 kilometres long (more than 50 miles). Imagine!
And finally, all this beauty and workability is not ephemeral. All three noble metals will last not just a life time, but many lifetimes. They are strong, that is resistant to chipping, breaking, scratching, and they are very resistant to corrosion, distinguishing them from base metals that quickly rust.1
1 Silver will slowly tarnish over time when exposed to sulphur compounds. Careful too with chlorine on your gold, it can damage the metal over time and for that reason it is recommended that you remove your gold jewellery when in swimming pools and Jacuzzis (see also the article on 'Caring for Your Jewellery').