Gold

60000 usd/kg
Circularity potential
Very high
Strength
High
Production energy
Extreme
Stiffness
High
Embodied CO2
Extreme
Density
Extreme

Gold is revered for its properties: a combination of colour, corrosion resistance, weight and malleability. While it is biocompatible and suitable for implanting in the body (such as to repair or cap teeth as a dental alloy), and its superior conductivity is used in precision electronics applications, the majority ends up in jewellery and tableware.

Its resistance to corrosion and tarnishing sets it apart from other conductive and malleable metals, like copper and silver. Its high resistance to corrosion means that it maintains it performance over time, giving consistent and reliable results.

The purity of gold is measured in carats (ct or c), also karats (kt or k), and is defined by the % weight of gold in the metal: 24 ct pure gold, 23 ct is 95.8% gold, 22 ct is 91.7% gold, 21k is 87.5% gold, 20 ct is 83.3% gold, 19 ct is 79.2% gold, 18 ct is 75% gold,14 ct is 58.3% gold and 10 ct is 41.1% gold.

For parts that are not required to be solid gold, it can be plated onto the surface of another metal. For example, in applications where it is not practical to use gold, such as for weight or strength reasons, or if it would be too expensive or unnecessary.

The carbon footprint and embodied energy (resource use) are eye-watering – much higher than other engineering materials. They are surpassed only by rhodium (Rh) and platinum (Pt). Much of this is the result of the mining practices and energy consumed during refinement and production. Gold is difficult to extract from its ore.


Sustainability concerns
Non-renewable ingredients
Raw material generates polluting by-products
Potential conflict commodity (3TG)


18 ct rose gold comprises 75% gold mixed with 25% copper (Cu). It may also contain some silver (Ag) and other alloys. It is harder than yellow gold with a reddish colour that is determined by the proportion of the alloys. It is mainly used for jewellery and tableware.


Design properties
Cost usd/kg
45000
Embodied energy MJ/kg
9600
Carbon footprint kgCO2e/kg
160000
Density kg/m3
15300
Tensile modulus GPa
77
Tensile strength MPa
550-880
Hardness Mohs
3.5
Melt temperature ºC
897
Thermal conductivity W/mK
300
Temperature min-max °C
-250 to 400
Thermal
good conductor
Electrical
good insulator