Gold quality and color
Gold has an extraordinary heritage with unique qualities. Gold is resistant to rust, tarnish, and corrosion. Although gold is solid, it's also the most complicated of all precious metals.
Gold is measured in KARAT units.
(There is no connection between the carat which is a unit of weight and the diamonds)
Since gold is an expensive and soft material, it is necessary to mix it with alloys to give its properties, such as hardness and color.
There are five commercial qualities:
9K Trademark 375.
It consists of 37.5% pure gold + 62.5% metal alloy.
14K Trademark 585.
It consists of 58.5% pure gold + 41.5% metal alloy.
18K trademark 750.
It consists of 75.0% pure gold + 25% metal alloy.
21K Trademark 916.
It consists of 91.6% pure gold + 8.4% metal alloy.
24K trademark 999.9.
It consists of 99.9% pure gold.
Yellow Gold - Yellow is the natural color of gold, but yellow metals are also added to yellow gold to give it the known color. Copper and silver will usually be added to yellow gold. The ratio of silver to copper is accepted worldwide. This ratio determines the hue of gold. But this is also why sometimes you can see jewelry that is different in color even though they both have the same carat.
White Gold - Natural gold is yellow. So metals with a white undertone such as silver, palladium, or zinc are added to the yellow gold. Still, gold will have a soft yellowish tint. Hence the jewel is dipped in rhodium that composes in the electrolysis process with the outer layer of gold. The jewel gets a bright white color.
Rose Gold -To create a piece of jewelry made of rose gold, a high copper percentage is added to the yellow gold. As more copper is added, the gold color gradually turns more reddish.