Before explaining the types of gold, we’d introduced the concept of Karat at first. The karat (US spelling, symbol K or kt) or carat (UK spelling, symbol C or ct) is a fractional measure of purity for diamond or precious metal like gold. When the karat is used to measure gold, it represents how much pure gold element containing in. In this concept, the whole metal is divided into 24 parts and 24K refers to the purest gold. For example, 18K gold jewelry represents that 18/24, or 3/4 of its raw materials consists of gold, while the rest are the base metal.
Base metal plays a very important role in changing the color, durability, and solidity of gold. Also, another obvious benefit is that the gold becomes more affordable. According to this finding, metalsmiths developed different types of gold.
Based on different colors, the gold is classified into yellow gold, rose gold, white gold, green gold, blue gold, and even black gold.
When we talk of gold, the first thing that comes to our mind is usually a glorious yellow tone because 24K gold shows in this color. However, not all the yellow tone gold is pure gold. Other golden alloys mixed with metals such as silver, zinc, and copper could represent a yellow tone as well. For example, 18K yellow gold normally consists of 75% gold, 12.5% copper, and 12.5% silver. Or, in order to make it look darker, copper content would be increased to 15%.
It should be noticed that the copper-based alloy would also come with golden color and luster, such as brass and bronze. Brass is a bright yellow consisting of 67% of copper and 33% of zinc. If the content of zinc drops, it would turn to be reddish. There are more than 60 types of brass on the record of European Norm Standards. Brass is a thrifty, attractive metal with a golden tone and it is malleable and easy to manipulate so it can be fabricated or cast. Bronze, consists of 12% tin (or other metals) and 88% copper, having a warm, brown tone.
White gold is an alloy consisting of gold and other metal like nickel, silver, or palladium. The common composition of 18K white gold is 75% pure gold and 25% silver and nickel. Compared to silver or nickel, palladium is an expensive precious metal so it is widely used in white-gold making.
People would get confused when they have to choose jewelry from silver, white gold, and platinum because they all look like silver-tone. Well, the biggest difference is the price. There is no doubt that white gold is more expensive than silver, whilst it is far lower cost than platinum. Considering durability and rigidity, platinum plays better than white gold, while white gold is better than silver.
Rose gold, also known as pink gold or red gold, is a result of alloying pure gold with copper, as copper has a red tinge to it. The shade of rose gold can also vary greatly, depending on the proportion of copper blended with the gold. The greater the content of copper, the redder the final color is. A common combination in jewelry for rose gold is 75% gold mixed with 25% copper.
A key point to keep in mind with white and rose gold is that since gold must be combined with other metals to transform the color, it is impossible to achieve “pure” (or 100% / 24k) white or rose Gold.
According to the research, green gold originated from Crete Island and started to be used in 860 BC. It is a naturally-born alloy made up of gold, and silver. Silver endows the green tone with the extremely light green tone. In most cases, you’d hardly notice the green-tone hiding in the gold without being told what it was, because the natural green-gold shows in greenish-yellow instead of pure green. In order to enhance the green tone, people added cadmium into the composition, while this kind of green gold is not accepted in daily use but just for appreciation as the cadmium is highly toxic.
Light Green Gold (18K)
Gold 75% Copper 23% Cadmium 2%
Deep Green Gold (18K)
Gold 75% Silver 15% Copper 6% Cadmium 4%
Black gold is another uncommon type of gold in daily life. There are five ways of endowing the gold with a black tone.
Oxidation - Metalsmiths would use a special acid on the gold surface to create a darkening look.
Blackening - The surface of gold would be painted with a paint-like liquid. Then the liquid would gradually slip into the nooks and crannies.
Black enamel-Enamel is baked onto the surface of the jewelry, much like similar liquids are applied to ceramic pieces. The result is a hard, smooth, and shiny covering.
Black Rhodium Plating- It is the rather common method used for black gold, where the surface of the gold is plated with a black finish, normally with black rhodium or ruthenium. However, the obvious disadvantage is that the color wears off over time.
Gold &Cobalt Alloy - Mixed with another metal such as cobalt, usually to the ratio of 3 parts gold to 1 part metal, a black tone could appear on the gold.
No doubt that it is a brand-new type of gold. To make a slight bluish-tone gold, gallium or indium would be added to the compound. As for rich bluish-tone gold, it could be made by alloying with ruthenium and rhodium.