GOLD COLORS IN JEWELRY
Have you ever been confused by the terms white gold, green gold, and rose gold? All real gold is yellow, isn't it, so how do other colors fit in -- are they imitations? No, they aren't imitations at at all, those 'other' colors of gold are alloys, new metals that are created by combining two or more different metals.
PURE GOLD AND COLORATIONS
The pure gold is slightly reddish yellow in color, but colored gold in various other colors can be produced. Colored golds can be classified to three groups:
Alloys with silver and copper in various proportions, producing white, yellow, green and red golds; typically malleable alloys
Intermetallic compounds, producing blue and purple golds, as well as other colors. These are typically brittle but can be used as gems and inlays
Surface treatments such as oxide layers
COMMON COLORS IN JEWELRIES
Due to their malleability, the most common colors are white, yellow and red (also called pink or rose).
A mix of natural gold and color saturated alloys is what gives yellow gold jewelry it's color. The alloys that are most commonly used are copper with red hue and silver with green hue. This unique mixture of pure gold, silver and cooper gives yellow gold it's distinct color.
White gold is an alloy of gold and at least one white metal, usually nickel, manganese or palladium. Like yellow gold, the purity of white gold is given in karats. Even if palladium is more expensive than nickel and manganese, this particular alloy generally don't cause any allergic reaction.
ROSE, RED AND PINK GOLD
Rose gold is a gold and copper alloy widely used for specialized jewelry. Rose gold, also known as pink gold and red gold, was popular in Russia at the beginning of the nineteenth century, and was also known as Russian gold although this term is now obsolete. Rose gold jewelry is becoming more popular in the 21st century and is commonly used for wedding rings, bracelets, and other jewelry. 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. Pink gold uses the least copper, followed by rose gold, with red gold having the highest copper content.
Black gold is a type of gold used in jewelry. Black-colored gold can be produced by various methods:
Electroplating, using black rhodium or ruthenium. Solutions that contain ruthenium give a slightly harder black coating than those that contain rhodium.
Patination by applying sulfur- and oxygen-containing compounds.
Plasma-assisted chemical vapor deposition process involving amorphous carbon
Controlled oxidation of gold containing chromium or cobalt (e.g. 75% gold, 25% cobalt). A range of colors from brown to black can be achieved on copper-rich alloys by treatment with potassium sulfide.