Gold has had an inestimable effect on human history. It has been crafted, mined, worshipped, plundered, fought over and traded for thousands of years. Today, the search for gold is as eager as ever, despite the vast stocks stored away in underground bunkers. So why has gold held this fascination for humanity?

Its initial attraction is its color, an eye-catching and characteristic bright yellow with a soft metallic glint. Gold’s pleasant ‘feel’, a combination of its density (19.3 grams per cubic centimetre when pure) and coldness, cannot be duplicated by any other metal. Furthermore, gold can be hammered into very thin sheets or leaves, drawn into wire, cast, carved, polished, heated without tarnishing and easily combined (alloyed) with other metals.

Gold also conducts heat and electricity, reflects light and is untouched by nearly all acids, a property which led alchemists to christen it the noble metal. This combination of properties makes gold very stable in its natural metallic form, and also gives it many uses in electronics, ornaments, jewelry and advanced technology.

The color of gold is directly related to its purity. Crystallised gold and silver have the same atomic structure and their atoms are nearly identical in size, so that natural alloys of gold and silver are common.

Pure, or 24-carat gold, is the brightest yellow, but as the amount of silver increases the color becomes paler. Pale gold containing more than 20 per cent silver (corresponding to about 20-carat gold or less) has been called electrum. Trace amounts of copper, iron and palladium can also substitute in gold. Man-made alloys of gold with rhodium, iridium or palladium, intended to give gold greater hardness when used in jewelry, have been given names such as ‘white gold’. The carat scale is commonly used in jewelry, while in mining, an alternative scale uses ‘fineness’ of gold, where a figure of 1000 corresponds to pure or 24-carat gold. Credits: By Dr Bill Birch, Senior Curator, Geosciences, Museum Victoria