Gold is a rare precious metal, with a remarkable combination of chemical and physical properties. The name gold derives from the Old English word for yellow, ‘Geolu’ and gold is the only yellow metal. Pure gold does not oxidize under normal conditions, meaning that it will not corrode or tarnish. Gold’s special physical properties of high electrical conductivity and chemical inertness make it an excellent and reliable conductor, particularly in harsh environments with extreme temperature ranges. Gold finds uses in many technical applications, in the manufacturing of PCB boards and in electrical circuits. It is amazingly malleable and therefore lends itself especially for jewellery making.
The purity of gold is measured in karats. The term “Karat” is different from the unit of measure “Carat”, which is used to measure gemstone weights. The purity of gold in karat terms determines its value. “Karat” is derived from the word “Carob” and stems from ancient trading times, when the seeds of the Carob tree were used as a reference weight to measure the weight of precious metals. Pure gold is very soft and malleable and therefore needs to get alloyed with other metals to achieve the strength and hardness that is required to create useable objects. The mixing of gold with other metals also changes its colour. 24 karat is 100 % pure gold, and is more expensive and less durable than gold that is alloyed with other metals.
Gold Purity for The Most Commonly Used Karats:
24 Karat – 24K Gold with 100% purity
22 Karat – 22K Gold with 91.6% purity
18 Karat – 18K Gold with 75% purity
14 Karat – 14K Gold with 58.33% purity
24 karat gold is soft pure gold without any alloys and features a deep yellow colour with a rich luster. Gold of lesser karats (22K-14K) are all alloyed with a combination of silver, copper, nickel and zinc. These alloying elements add strength, but they can also impact the depth of the colour. Any gold alloy combination below 14 Karat will render a dull and pale colour. For beauty, durability, and wearability 14K and 18K gold are highly recommended.
In its pure form, gold has a high metallic yellow luster, but when alloyed with other metals, such as silver, copper, zinc, nickel, platinum, palladium, etc. it displays various colour shades like white, pink/ rose and green.
Yellow gold is the most frequently used gold colour and is considered timeless colour. It is usually alloyed with silver and copper. Depending on the karat gold (14K, 18K or 22K), the color of yellow gold may vary from a softer shiny yellow to a bright rich yellow luster. This is due to the varying alloy combinations. Yellow gold is the ideal gold colour for setting warm coloured gemstones. For instance, when setting emeralds, it is recommended to set the gemstone into a yellow gold setting, as the warm colour of the gold will make the emerald appear deeper green and more precious.
White gold is harder than yellow gold and features a bright and shiny luster. It is often alloyed with a high percentage of silver, or a mixture of other white precious metals, such as palladium. Some white gold alloys are created by the use of nickel. This metal is known to cause allergies, which manifest themselves in the form of skin rashes and itchy skin. Navrathan uses nickel-safe white gold alloys that meet international consumer protection standards. White gold is never fully white and to improve the whiteness it is electroplated with rhodium. Rhodium is a platinum group metal which features an exceptional whiteness and hardness. Rhodium plating therefore not only makes the jewellery piece look whiter, but it also provides the surface with a layer of increased hardness, which in turn provides a higher degree of scratch-resistance.
Pink / Rose Gold
Pink gold or rose gold does not exist in nature. Instead, it is created by mixing the yellow gold content with copper, silver and zinc. The higher the copper concentration in the alloy is, the deeper will be the rose colour of the resulting gold. Rose gold is available in a number of purities. The higher the concentration of the non-gold components of the alloys are, the paler is the resulting rose gold colour. The colour of rose gold ranges from a deep, almost copper-red colour, to a light radiant blush pink depending; on the recipe of the specific gold alloy. Pink gold alloys are very fashionable and are the preferred gold colour for fancy colour pink diamonds as well as pink sapphires and tourmalines. The surrounding pink gold colour in a setting bounces its colour reflection onto the gemstone and makes it appear more deeply saturated and hence more valuable.
Green gold is a popular gold colour in the US and supports fair skin tones very well. It is not particularly popular in Asia, because the cultural preferences there are more geared towards deeply saturated gold tones. Green gold is an excellent base alloy for fired enamels, because it consists only of precious metals and hence doesn’t tarnish under the high firing temperatures required for the creation of fine enamel surfaces. For the creation of green gold, pure gold is alloyed with silver to achieve a green gold colour. Green gold is often used as a contrast colour in multi-colour jewellery designs and adds a spot of a different and unusual colour to an otherwise rather traditional appearance.