The development of civilisation owes a great deal to the discovery and use of silver. It has found application in many places – from the ornamental to the highly practical. Silver is an excellent conductor of both heat and electricity – in fact, it conducts the former better than any metal and the latter better than any other element on the periodic table – and so remains valuable to modern electronic manufacturers who use it extensively in electrical contacts and circuit boards. But for most of human history, silver along with gold served as a signifier of wealth.
What Do we Use Silver for?
For most of civilisation, silver was most often used in coinage. For thousands of years, it was the standard among systems of currency. Silver coins were used by civilisations in ancient Greece, Rome and Persia, (in the form of the Drachma, Denaraius and Dirham respectively), as well as in China.
But why did all of these peoples independently conclude that silver was a suitable material for money? The answer lies in the value of the metal. Like gold, the value of silver allowed merchants to easily transport large quantities of wealth and currency from place to place, in a way that iron currency would not be able to do.
Silver has a number of other qualities which make it a suitable form of currency. The value of silver is both stable and intrinsic. It does not decay and can be easily divided into smaller pieces and reformed again into larger ones. For these reasons, among others, silver remained a standard until the 20th century, when it was supplanted by centrally-issued currencies with negligible intrinsic value.
Silver has also long been used in the creation of plates, cutlery and tableware – so much so, in fact, that such objects made from silver have their own special name – silverware. Silverware is, more often than not, made from Sterling Silver, which is an alloy comprised of over 90% silver, with the remainder made from copper.
This alloy will typically be covered with a fine coating of pure silver, which endows it with the shining lustre which typifies silverware. For this reason, silverware must be carefully polished by hand – too much abrasion will wear away this top layer, to reveal the comparatively dull material beneath.
The care of silverware would in large Victorian households, be entrusted to a specialist, such as a butler, who would ensure that each item was properly cared-for and displayed on the table. Today, this duty is typically only carried out on very special occasions hosted by organisations like the military.
As it is both expensive and difficult to properly maintain, silverware is not widely-used today. Instead, it is often presented as a gift. It has long been a tradition that a newly-christened baby, for example, be presented with a silver Quaich or another container. There exist a few artisan companies who are capable of providing specially-crafted silverware for such occasions; their work often comes engraved with initials or other markers in order to make it perfectly suited to a particular gift. Silver is also suited to jewellery. Not only does it look attractive, but it becomes easily malleable at relatively low temperatures and so can be spun into a variety of shapes by a skilled metalworker.
The surfaces of glass objects are also sometimes treated with silver. This is done for several reasons. In windows, it serves as an insulator. A layer of silver, only a few nanometres thick, can be applied to the surface of the window in order to create a glazing effect. As this coating is so thin, the cost of the silver itself is miniscule.
In mirrors, particularly those in telescopes – silver serves as a reflecting agent. In this application, it is preferable to aluminium, as it is better suited to reflect certain sorts of infrared radiation. It also emits a great deal less of this radiation itself – thereby reducing the amount of noise present on the image. In creating high-precision infrared images of the night sky, silver is therefore of enormous value.
In photography, silver – in the form of silver nitrate and halides – was used as a means of developing images. Since the introduction of the digital camera and its incorporation into the mobile phone, the use of silver in this environment has plunged – though this change has also heralded in an increase in the use of silver for batteries and electronics.
Silver is rarely used in normal batteries, as other materials are far more economical. In certain applications, however, silver-oxide batteries are favoured. These might include smaller devices which require their own power source, such as hearing aids, where a silver-oxide battery’s longer life and superior energy-to-weight ratio lend it an advantage over other sorts of batteries.
How is Silver Made?
Now that we’ve seen what silver might be used for, let’s take a look at how it is created. Silver is typically found in the ore that contains other valuable metals, among them lead, copper, gold and zinc. These metals must first be extracted from one another if they are to have any application and value. The method through which this is done varies according to the metal; silver is rarely sought for its own sake and comes rather as a by-product of attempts to refine other precious metals. Throughout history, there have been a myriad of ways in which silver has been extracted from its ore. Let’s take a closer look at some of them.
As these metals have different properties, they can be extracted from one another by exposure to certain conditions. As some, for instance, have different weights and melting points, silver can be extracted by exposing the ore to varying levels of heat.
The earliest forms of extractive metallurgy involved smelting. Contrary to popular belief, smelting does not involve simply melting the metals of an ore and splitting them apart from one another. In an ore, many metals are fused together in a chemical compound, which can only be broken down into its constituent parts by performing a certain chemical reaction.
In the case of zinc-bearing ores, the metals can be extracted by melting the ore and then allowing the liquid metal to solidify. At the top will form a crust of zinc and silver, which can then be extracted and separated into its constituent parts using a process of distillation.
In the case of copper-containing ores, electrolysis can be employed. The ore is placed in a cell containing two conversely-charged electrodes: an anode and a cathode. As current passes through the ore, copper will be drawn to the cathode, while the remainder will be drawn to the anode. The remainder can then be smelted to remove any impurities and then subjected to another round of electrolysis, through which the silver can be extracted.
Mercury amalgamation came to be widely-used in the sixteenth century, when the ‘patio process’ was invented in Mexico. It involves the use of mercury to draw the silver from an ore and comes in many different forms – the most widespread of these is the heap leach.
The heap leach is a way of processing low-grade ores cheaply and for this reason it is used extensively today. It employs a series of chemical reactions designed to draw the silver from the ore, and its principle ingredient is cyanide.
And that is how you make silver!