Gold

Gold is the absolute oldest of all metals. It doesn't corrode, tarnish or rust, so you can count on it to always stay gorgeous. Despite being a strong metal, it is still more "flexible" than the other precious metals. 

 

The purity of gold in an alloy is expressed in karats (K). Karat purity is measured as 24 times the purity by mass. The Karat system is increasingly being complemented or superseded by the millesimal fineness system, in which the purity of precious metals is denoted by parts per thousand of pure metal in the alloy. To keep gold solid and suitable for jewellery, pure gold is commonly mixed with different metals to increase its strength.

 

  • 24K (karat) or "Chuk Kam" is defined as 99.0% gold minimum with a 1.0% negative tolerance allowed. It is very soft and therefore more rarely used in jewellery.
  • 18K (karat) gold is made up of 75% gold and 25% other metals (or 18 parts gold to 6 parts alloy). It is commonly used in fine jewellery.
  • 14K (karat) gold contains 58.3% gold (or 14 parts gold to 10 parts alloy) This is the most common form of gold found in jewellery where strength matters.
  • 10K (karat) gold is made up of 41.7% gold (or 10 parts gold to 14 parts alloy). This is the minimum amount of karats an items needs to be classified as real gold in the U.S.

 

While pure gold is yellow in color, colored gold can be developed into various colors. These colors are generally obtained by alloying gold with other elements in various proportions.

 


 

Yellow gold is the most common form of gold found in jewellery and is usually mixed with copper and silver. Its color depends upon the amount of pure gold in the alloy.

 

 Rose gold is a copper and copper mixture that often appears in custom jewellery due to its distinctive reddish color. It is also known as pink gold and red gold. Sometimes it is also referred to as Russian gold, because it was very popular in the early XIXth century. What makes rose gold red is the amount of copper in the alloy - the more copper in the mix, the more red the jewelry appears to be. Since rose gold is an alloy, there is no such thing as "pure rose gold". 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". The highest karat version of rose gold is also known as crown gold, which is 22K. 18K red gold may be made of 25% copper and 75% gold. For 18K rose gold, typically about 4% silver is added to 75% gold and 21% copper to give a rose color. 14K red gold is often found in the Middle East and contains 41.67% copper.

 

 

 White gold is composed of yellow gold and at least one other white metal alloy. White gold coming from European countries no longer contains nickel. Nickel is usually substituted with palladium. A nickel-free white gold is more expensive than yellow gold. The piece is then plated in rhodium, which gives it a shiny white color. Over time, however, rhodium plating wears off naturally and the color begins to fade. As a result, white gold pieces must be re-plated in rhodium once a year, on average, in order to maintain their color.

 

  Black gold is an other type of gold used in jewellery. Black colored gold can be produced by various methods:
  • Electroplating, using black or 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.
  • More recently a laser technique has been developed that renders the surface of metals deep black

 

Caring For Gold Jewellery

To keep your gold shiny and free of scratches, store it in a soft cloth bag or a fabric-lined jewelry box. Make sure to keep gold jewelry away from harmful chemicals such as bleach, ammonia and chlorine. Always use a soft cloth to dry your jewelry, never paper towels.