Physical properties

• Gold is the most malleable and ductile of all the metals, and one of the softest and heaviest
• It is an excellent conductor of heat and electricity
• It is resistant to attack by air, heat, moisture and most solvents
• Gold dissolves in aqueous mixtures containing halogens (such as chloride, bromide and iodide) as well as some oxidising mixtures such as alkaline cyanide solution and aqua regia (a mixture of hydrochloric and nitric acids)
• Native gold generally contains impurities such as silver (Ag), copper (Cu) and iron (Fe) with traces of bismuth (Bi), lead (Pb), zinc (Zn), antimony (Sb), tellurium (Te), mercury (Hg), tin (Sn) and platinum (Pt)
• The purity or fineness of gold is expressed in parts per 1000 and can range from about 500 (50% impurity) to 900 (10% impurity) for vein gold, and from approximately 500 to 999 in alluvial gold
• Gold can be alloyed with various metals to give unique properties such as red gold (Cu), green gold (Cu and Ag) and white gold (Ni, Zn or Pt metal). The most common naturally occurring alloy is electrum, which is pale yellow and contains >20% Ag. The gold content (by weight) of an alloy is described in carats; pure gold (24 carat) is used in the Australian Nugget coins; 18 carat gold is 18/24 pure gold; 6/24 is an alloy metal

Uses

• Because of its rarity, durability, colour and chemical inertness, gold has been used throughout history for the payment of goods and services and is now the basis for international monetary exchange
• Global uses of gold include; jewellery (51%), gold coins and bars (25%), central bank reserves (15%), electronics and industrial (7%), global backed exchange traded funds (1%) and dental and medical (1%) (DIIS 2019)
• The high density of gold allows large quantities to be stored in a small space - 1 t occupies only 0.05 m³. The Perth Mint created a one tonne gold coin in 2011
• Global uses of gold (tonnes):