Gold is the protagonist of jewelry materials. Gold jewelry can be traced back more than 6000 years! Nowadays, gold comes in various forms, colors, and karats – each has its unique properties.
Of course, like all other precious metals, gold is far too soft to be used as jewelry for everyday wear. Instead, we use alloys. Gold alloys are a mixture of gold and one or more other elements, typically silver, copper, nickel, and zinc. These help to improve the strength, hardness, durability, and workability (for manufacture) and to tune the color of the gold alloy.
What does Karat mean?
Karat is a measure of fineness (proportion of precious metal by weight) in a gold alloy, with 24K being essentially pure gold. The most common fineness for jewelry is 18K, then 14K, and 10K. 24K and 22K are sometimes sold, but these are not durable enough for everyday wear in use for rings, necklaces, etc.
N.b. This is different from carat, which is the measure of the size/weight of a gem.
Karat | Fineness | Proportion of Gold (by weight) | Comments |
24 | 999 | 99.9% | Very soft, strong yellow color. Only common in the Asian market. |
22 | 916 | 91.6% | Very soft, strong yellow color. Only common in the Asian market. |
18 | 750 | 75.0% | Common "premium" hallmark. Excellent Rose, white and yellow colors are available. Scratches quite easily. |
14 | 585 | 58.5% | High-quality hallmark, most popular. Good Rose, white and yellow colors are available. Excellent durability |
10 | 417 | 41.7% | Excellent value for money. High durability, slightly inferior colors and sometimes issues with skin allergies |
9 | 375 | 37.5% | Excellent value for money. High durability, slightly inferior colors, and sometimes issues with skin allergies |
There are some general rules associated with properties and karatage:
Tarnish resistance decreases as the karat falls,
Appearance is duller in white gold as the karat falls, and lower karat yellow and rose golds have a deeper hue,
Hardness, wear resistance, and durability increase as the karat falls.
We recommend you always ask a reputable jeweler about the metal before purchase. All jewelry should have a hallmark or stamp to indicate what it is and its fineness (or karat, for the specific case of gold). This can either be a symbol or a number, such as "14K" or "585". The requirements for hallmarking vary from country to country.
We recommend only buying expensive jewelry from a reputable jeweler or manufacturer.
Skin Allergies and Gold
Except in very rare and specific circumstances, pure gold is considered hypoallergenic. There are a few specific cases where gold can cause a skin allergy.
Gold alloys, on the other hand, can often cause contact dermatitis (skin allergies) due to the presence of certain "base" metals. The common cause is nickel, which is often present in large quantities for many white gold alloys.
The nickel content in most 18K and 22K alloys is too low to cause skin irritation, except for the most sensitive of skin. As for 18K Nickel-white golds and all lower karat golds, they can often be problematic. If you have sensitive skin, it is often wise to choose nickel-free alloys, e.g., palladium-white gold alloys.
The color of Gold
Pure gold is a stark yellow color. To many people, its color is unfamiliar due to the rarity of 24K gold jewelry. There is no such thing as white or rose gold, but rather white-gold and rose-gold alloys.
The color and hue of gold jewelry can be changed by alloying additions. Subtle changes in composition can give precise tuning of color. For example:
Nickel and Palladium are strong bleachers, turning gold white
Silver gives gold a greenish hue
Copper gives gold a reddish hue
Selecting the color of gold for your jewelry should be based primarily on your preference. There are some minor differences in properties which are explained below.
White Gold
White gold has become extremely popular. Two main types of white gold alloys are Nickel-white gold and palladium-white gold. These are gold alloyed with nickel and palladium, respectively, as these elements bleach the color.
Palladium-white golds are preferred because they are hypoallergenic; the absence of nickel means they do not cause skin irritation and contact dermatitis. However, they are more expensive.
It is important to be aware that white gold alloys are sometimes coated with Rhodium to give them a bright-white color. Over time, this will wear away, and the bright white color will be irreversibly lost. The white gold underneath will have a duller and yellowish appearance compared to the rhodium. Higher karats tend to be duller, as there are fewer "bleaching" additions. A jeweler may be able to reapply the rhodium coating.
Rose Gold
Rose gold was first introduced to the Russian Imperial court by Carl Fabergé himself. In recent years, it has become extremely popular. Rose and Red gold are predominately gold-copper-silver alloys, with copper giving the reddish hue. One often has to move to a lower karat to achieve darker colors, such as 18K to 14K. This has the added advantage of improved durability.
Other colors of Gold?
You may often hear of other colors, such as purple and blue. These are made by mixing gold with aluminum (purple), indium, or gallium (blue). These materials are extremely brittle, so they can only be used for decorative purposes. They remain an area of research.
Gold-plating (incl. Vermeil/silver-gilt)
Gold plating, rolling, or filling is also common, where a thin layer of gold is coated onto an alloy. Gold fill lasts much longer than plating, as the layer applied is much thicker (it must be 5% of total weight), followed by rolling (2.5% by weight) and then plating.
Vermeil, or silver-gilt in English, is sterling or pure silver which has been gilded with gold (coated with a thin layer). Besides being cheaper, silver-gilt objects are far lighter and have a long-standing history of use. In the US, gilt must have a gold content equivalent to 2.5 micrometers of fine gold.