|3 Colors of Gold|
But What Makes It Pink?
Pure 24k gold is yellow, and is very soft. It is alloyed with other elements to produce colors and other karats. The most common karat grades of gold, in addition to pure 24K (100% gold), are 22K (92% gold), 18K (75% gold), 14K (58% gold), 10k (41% gold) and 9K (38% gold). For example, alloys which are mixed 14 parts gold to 10 parts alloy create 14K gold, 18 parts gold to 6 parts alloy creates 18k, etc.
There are hundreds of possible alloys and mixtures, but in general alloying gold with silver will color gold white, and the addition of copper will color it red (or pink). A mix of around 50/50 copper and silver gives the range of yellow gold alloys the public is accustomed to seeing in the marketplace. A small amount (0.2%) of zinc is sometimes added to give the gold added strength and hardness.
- the Au-Ag-Cu system, producing white, yellow, green and red golds;
- the "intermetallic" compounds, producing blue and purple golds, as well as other colors. These are typically brittle.
- the surface oxide layers, such as black gold; the colored surface is prone to wear off.
Although the names are often used interchangeably, the difference between red, rose, and pink gold is the copper content – the higher the copper content, the stronger the red coloration. A common alloy for rose gold is 75% gold and 25% copper by mass (18k). But it's also common for 18 karat rose gold to typically add about 4% silver to 75% gold and 21% copper to give a rose color. Since rose gold is an alloy, there is no such thing as "pure rose gold". The highest karat version of rose gold is also known as "crown gold", which is 22 karat. 14 karat red gold is often found in the Middle East and contains 41.67% copper.
During ancient times, due to impurities in the smelting process, gold frequently turned a reddish color. This is why many Greco-Roman texts, and even many texts from the Middle Ages, describe gold as "red"!
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