Gold: 24 Karat or 999

Gold is the most coveted metal in the history of mankind. Since ancient times people have been fascinated by the metal’s beauty and fitness for jewelry use—its malleability as well as its resistance to corrosion, oxidation, and scratching. Examples of elaborate gold workmanship have survived from early civilizations spanning the globe: Incan, Mayan, and Aztecan in South America and Central America; Egyptian, Minoan, and Assyrian civilizations of the Middle East; the Etruscan civilization covering the territory of modern Italy; Harappan in India; and Sarmatian in the southern Ural mountains.

Today gold in its pure form is rarely used to produce jewelry.  Most 24-karat gold is sold as investments to world governments and central banks as well as private investors. Twenty-four-karat gold is too soft and not durable enough to use for jewelry. Jewelers use different alloys, combining gold with other metals to give it more hardness. For example, the most popular grade of gold purity in the United States is 18-karat, meaning three-quarters of the alloy is gold and one-quarter is a mixture of copper and silver.

Mixing in silver and copper is a bit of science—if too much silver is added, the gold will show a green tinge. On the other hand, mixing in too much copper will give gold a red tinge (so-called “rose gold”). Addition of nickel or palladium overpowers the distinctly bright yellow color of gold, producing what is known as “white gold.” Mixing other metals with gold produces a variety of colored golds, such as green gold , pale yellow gold , yellow gold, red gold, and white gold.

Gold purity is measured in karats (known as “carats” in countries of the British Commonwealth) and refers to the amount of pure gold present in the jewelry. Twenty-four-karat gold is considered to be pure gold, or 99.9% pure to be exact. Dividing the karat unit by 24 will provide the percent of pure gold in the jewelry. Thus, if you are wondering how much gold is in the 18-karat wedding band you are wearing, divide 18 by 24 to get 75%. Your wedding band gold is 75% pure.

In Europe gold purity is expressed using millesimal fineness, parts per thousand of pure metal by mass in the alloy, rounded to three digits. Gold rated 24-karat or 99.9% pure in the United States would be stamped “999” in Europe.

The table below provides translation of the U.S. gold purity system into the European one.

Gold Content and Notation
USA Karat Stamping Parts Gold Gold % European Gold Purity Stamp
24K 24 / 24 99.9% 999
22K 22 / 24 91.7% 916 or 917
18K 18 / 24 75.0% 750
14K 14 / 24 58.3% 583 or 585
12K 12 / 24 50.0% 500
10K 10 / 24 41.7% 416 or 417
9K 9 / 24 37.5% 375

Stating the obvious, the purer the gold content in a piece of jewelry, the more valuable it is. Thus, with the current price of gold hovering around $900 per troy ounce (equivalent to 31.103 grams) the price difference between 24-karat gold and 18-karat gold would be $225 per troy ounce. One troy ounce of 18-karat gold would cost 75% of $900, or $675.

Jewelers use special X-ray fluorescence instrumentation to test the karat grade of precious metals and jewelry. These machines determine the gold karat measurement without damaging fine jewelry. More sophisticated equipment can also determine proportion of gold, platinum, silver, palladium, rhodium, and other precious and semi-precious metals in the alloy composition of gold jewelry.

Choice of the metal for the ring setting can be drive by different considerations:

  • Beauty of various metals in the eye of a beholder (e.g. gold vs. platinum) – some people prefer the richness and opulence of yellow gold, while others – the quiet nobility of platinum
  • Health considerations can come into play as well – by some estimates as many as one in four women may have an allergic reaction to nickel, often contained in what is known as “white gold” (an alloy of gold and nickel)
  • If you think of buying a diamond of a lower color grade (e.g. grades K through Z), you can mask that slightly yellow hue of the diamond by using a well-known trick of the trade – using the matching color of the metal (yellow gold) for the ring setting. Yellow metal makes slightly yellow or brown diamonds appear more colorless, while darker yellows and browns look darker and richer. White metal makes slightly yellow or brown stones look more yellow or brown (typically in an unpleasant sort of way) but enhances the color of blue stones. So, if you go for a diamond below K-color grade (GIA grading classification), think about buying a yellow gold setting, rather than white gold or platinum.

Decision about the design of the ring setting could be an easy one or rather difficult. It could be easy if you decide to choose what more than three thirds of Americans prefer to go with – a prong setting with a solitaire diamond. Or it could be more difficult, if you do not like prong and would like to choose from the other seven designs of ring settings: bezel or semi-bezel, channel setting, pav?, flush, bar, or invisible.