All about gold Pure gold is what we call 24 karat gold, and is a bright yellow. It is also very, very soft- so soft in fact that it can be scratched using your fingernail. It is also expensive- selling now at a near high point of over $1000 US an ounce.
For the reasons above gold is almost never used in jewelery in its pure form. Apart from the bright yellow colour and the cost becoming astronomical very quickly, the fact that it is so soft does not lend itself to jewelery that will stand up to regular wear and tear.
Pure gold is melted and mixed or alloyed with other metals to help make it stronger. The amount of the other metals changes the karat. Gold that is equal parts pure gold and some other metal (a 50% blend) will be 12 karat gold- or 50% of 24 karat.
This is why different places have different laws as to what can legally be sold as gold. In most of Europe and Asia, you can old sell it as “gold” if it is more than 50% pure gold- so more than 12 karat. This is why 14karat is the most common gold available commercially in these places. It is hard enough to wear well, and mixed with enough other metals to bring down the price substantially. In North America is is common to find 10 karat gold which has, in reality, less than 50% gold content.
A rainbow of colours- but no white
Changing the type pf metal added to pure gold changes the colour of the metal. Adding silver leads to green gold. Copper to red or pink gold, iron to blue gold, and aluminum to purple gold. Each type of metal addition also brings with it new challenges. For example the silver in green gold leads to gold that can tarnish like silver. Purple gold is known to be very brittle and is better treated as an accent stone rather than the metal to hold a piece together.
Each type of gold changes colour in much the same way you would mix paints. Yellow gold plus shiny copper equals a reddish toned gold. You never actually remove the yellow colour- you just hide some of it with other hues. This is why a true white gold with that gleaming platinum-like finish does not truly exist. “White” gold is mixed mostly with nickel, an inexpensive white metal that helps to tone down that bright yellow colour. When mixed the result is a lovely buttery grey that is beautiful in it’s own right.
Commercial white gold jewelery is often plated with rhodium to give it that platinum like look that is currently so popular. Be aware that this coating almost always wears off of high traffic areas of jewelery leaving the grey yellow underneath it more visible. There are new white gold mixtures being brought to market that use other alloying metals, but they are not yet commonly available.