Fineness of Gold and Stamp

The fineness of a precious metal object represents the weight of fine metal therein, in proportion to the total weight which includes alloying base metals and any impurities. Alloy metals are added to increase hardness and durability of jewelry, alter colors, decrease the cost per weight, or avoid the cost of high-purity refinement.

Gold is malleable in its pure state. Other metals are added to strengthen it and in some cases to enhance color. An example is "rose gold" comprises gold and copper. 24 karat gold is very soft and highly prone to scratching and damage. And pure gold is also vastly more expensive than alloyed gold.

A karat is a method of measuring the purity of gold. It is the ratio between the principal alloy (Gold) and any added alloys or impurities. Karat is worked out using the following calculation: Karat = 24 times the pure mass divided by the total mass.

Here’s more information on karats:

Karat is a measurement of the ratio of gold to other metals or alloys.
Karats are measured on a scale from 0 to 24.
The higher the karat number, the more gold there is and the less other metal content.
Other metals and alloys could include copper, nickel (not common anymore), silver, or palladium.

With this in mind, 24-karat gold is the purest gold you can buy.

The total of pure gold and other metal adds up to 24, so:

18K gold is 18 parts gold mixed throughout with 6 parts other metal
14K gold is 14 parts gold mixed throughout with 10 parts other metal

Conversion between percentage of pure gold and karats:

33–62.50% = 14K (acclaimed 58.33%)
00–79.16% = 18K (acclaimed 75.00%)
66–95.83% = 22K (acclaimed 91.66%)
83–99.95% = 23K (acclaimed 95.83%)
95–100% = 24K (acclaimed 99.95%)

Number of Karats	Parts of Gold	% of Gold Purity	Millesimal Fineness	Stamp
10K	10/24	41.7	416/417	10K, Au417
12K	12/24	50	500	12K, Au500
14K	14/24	58.3	583/585	14K, Au585
18K	18/24	75	750	18K, Au750
22K	22/24	91.7	916/917	22K, Au917
24K	24/24	99.9	999	24K, Au999

“GF” means gold filled,
Beyond the purity, there are also a marking to indicate the additive metal for impure alloyed gold.

“GP” means gold plated.

To express the base metal, “Pd” means Palladium, “PT” or “PLAT” means platinum and “SS” or “STEEL” means stainless steel.

14K gold vs 18K gold

18K gold jewelry’s biggest advantage is its gold purity with more intrinsic value. The extra purity can be especially obvious in 18K rose gold or yellow gold, which tends to show a warmer and more vivid tone than in 14K gold jewelry.

And the higher purity level of 18K gold jewelry also makes it less likely to trigger skin allergies than 14K gold jewelry.

18K gold is more expensive than 14K gold jewelry because of higher gold purity. However 14K gold is more durable than 18K gold because of more alloyed metal added.

14K Gold Jewelry:

Pros

Durable than 18K gold
Relatively cheaper

Cons

Possible allergic reactions

18K Gold Jewelry:

Pros

High intrinsic value. Warmer and more vivid tone.

Cons

Easy to scratch and more expensive.

Color of Gold

Gold typically comes in yellow, white, and rose. The white gold and rose gold are created by mixing gold with other metals.

Yellow gold represents the color of the natural color of the mineral.
White gold is created by mixing in palladium or nickel. It resembles silver but has a slightly brighter hue.
Rose gold is created by mixing in copper.

Solid Gold

“Solid gold” refers to any gold item where the inside of the item is not hollow. The karat mark still will denote the proportion of gold to other metal.

Plated or Vermeil Gold

Jewelry can be plated with gold by mechanical plating, electroplating, and other processes. Eventually, gold plating wears away. How soon depends on how often the item is worn and how thick the plating is.

”Gold filled,” “gold overlay,” and “rolled gold plate (RGP)” describe jewelry that has a layer of at least 10 karat gold mechanically applied to a base metal. These items should be marked with the term or abbreviation and the karat quality of the gold used (for example, 14K gold overlay or 12K RGP).
If the layer of gold is less than 1/20 of the weight of the metal in the entire item, any marking should state the fraction of karat gold (for example, 1/40 14K gold overlay).
“Gold electroplate” describes jewelry that has a layer (at least .175 microns) of at least 10 karat gold applied on a base metal by an electrolytic process.

Vermeil, a special type of gold plated product, consists of a base of sterling silver that is coated or plated with gold.

Gold-Filled

Gold-filled jewelry is composed of a solid layer of gold mechanically bonded to a base of either sterling silver or some base metal. The related terms "rolled gold plate" and "gold overlay" may legally be used in some contexts if the layer of gold constitutes less than 5% of the item's weight.

Most high quality gold-filled pieces have the same appearance as high carat gold. Gold-filled items, even with daily wear, can last 10 to 30 years though the layer of gold will eventually wear off exposing the metal underneath. The layer of gold on gold-filled items is 5 to 10 times thicker than that produced by regular gold plating, and 15 to 25 times thicker than that produced by gold electroplate (sometimes stamped HGE for "heavy gold electroplate" or HGP for "heavy gold plate", neither of which has any legal meaning and indicates only that the item is gold plated).

Gold Jewelry Maintenance

Clean it regularly. Gold jewelry wears and collects dirt easily, so it should be cleaned regularly. If you wear the jewelry every day, clean it at least once every other month. You’ll need two bowls of warm water, dishwashing soap, a lint-free cloth, and a toothbrush.
- Add a few drops of dishwashing soap to a large bowl filled with warm water. Gently place the jewelry in the water and let it soak for about 15 minutes.
- Pick up the jewelry and scrub it with the toothbrush. Pay special attention to the crevices where dirt can collect.
- Rinse the jewelry in the water bowl without the soap. Make sure you remove all soap residue.
- Gently blot the jewelry dry with a soft, lint-free cloth. Place the jewelry on the cloth and let it air dry for about 20 minutes.

Store it properly. Gold jewelry easily collects dust, especially pieces with a lot of crevices. If you aren’t wearing the jewelry on a daily basis, keep it in a small jewelry box. Try to keep it separate from other jewelry pieces that might cause scratching on contact.

Take it off when bathing. Gold jewelry will collect soap residue and potentially wear from hot water in a shower so make sure to take it off before bathing. Place is in a soft cloth where it won’t be damaged.