All About Gold

All About Gold

Is that a 10-karat diamond set in 19-carat gold? Or a 19-carat diamond set in 10-karat gold?

Okay, trick question. The words “karat” and “carat,” which sound alike, are a frequent source of confusion. So, with the price of gold at record highs and legions of people looking to turn their old jewelry into cash, it’s essential to know the precise meaning of such terms.

Karat with a “k” is a measure of purity for gold. The higher the number, the closer to pure gold it is. In the Western Hemisphere, gold purity is always referred to as karat with a “k”. The number preceding karat stands for the purity or fineness, as it’s also known, of the gold used. A “24” means pure gold, very rarely used for jewelry because it’s so soft.

In American usage, carat with a “c” is a measure of weight, used for precious stones. One carat equals 200 milligrams, whether the gem being weighed is a diamond, emerald, sapphire, natural pearl, or other jewel. (In Australia and most other British Commonwealth countries, “ct” is used as an abbreviation referring to gold.)

The Gold Standard

In the Western Hemisphere, gold is marked with one or two numerals plus “K” or “kt” (as in, 14K or 14kt gold). The British Commonwealth (other than Canada) uses the same numbers followed by “ct” or “c”. European countries use three numbers that indicate the amount of pure gold in parts per thousand.

Most gold jewelry is made in one of the following karat weights:

-10K, 10 ct, 416: 41.6 percent pure gold. This is the minimum standard that can be sold as gold in the United States. Jewelry made from gold of this purity is less expensive. It won’t tarnish easily, as the lower-karat gold, (8K and 9K), made in some other countries will.

-14K, 14ct, 585: 58.5 percent pure gold. The most popular standard of purity found in jewelry made in the United States and Asian pieces made for export.

-18K, 18ct, 750: 75 percent pure gold. The standard for high-end and custom-made jewelry, and the usual purity for all European jewelry except for some pieces intended for export.

-22K, 22ct, 916: 91.6 percent pure gold. Mostly found in jewelry made in India, Asia, and the Middle East. Because of the extremely small quantity of other metals used in the alloy, this high-karat gold is expensive, very soft and very yellow in color.

Gold jewelry is occasionally found in 8, 9, 12, 15, 16 or 17 karat, seen mainly in antique and vintage pieces and/or jewelry made outside the United States. To determine the purity of such an item, the math is simple. Each karat equals 1 part 24 of pure gold. For an item marked 15K, multiply the fraction 15/24 by 1,000. The answer is 625, or 62.5 percent pure gold.

The markings on damaged, very old, or badly worn jewelry may be hard to find and hard to distinguish. However if it’s gold, you should be able to find the hallmark or stamp using a jeweler’s loupe or a magnifying glass.

All That Glitters

Throughout history, gold has been highly prized. Because it has always been rare and expensive, various methods of placing gold over cheaper metals have been developed.

Many shiny pieces of jewelry as well as certain small objects – compacts and cigarette cases, for example – may bear a mark such as GF (gold-filled) or EP (electroplated), or they may be described with terms like “rolled gold” or “gold plate”. The processes place a microscopically thin layer of gold over brass or another base metal.

Gold filled, rolled gold, gold rolled and gold overlay are terms for an industrial process that uses high temperatures and great pressure to weld a thin sheet of gold (minimum 10K) to a base of brass or nickel.

Gold filled and gold-rolled jewelry is marked according to strict regulations. A typical markings on a gold-filled piece would be “1/20 14K GF,” meaning 1/20^th (or 5 percent) of the total weight of the item in 14k gold.

Rolled gold contains less than 5 percent gold, and will be marked something like “1/40 10K RGP.” That indicates that 1/40^th (or 2 1/2percent of the total weight) is 10K gold.

The thickness of the gold layer depends on how much wear the object is likely to get. Chains and eyeglass frames typically have 20 microns of gold, while watches and bracelets generally receive 30 to 150 microns. High quality gold-filled and gold-rolled objects remain bright for many years, and usually can be repaired if slightly damaged.

Gold plate refers to an electroplating process that deposits a layer of gold plate on top of a metal. Pieces made this way are less expensive than rolled or filled gold, but the gold layer is much thinner and less durable, and can’t be polished or repaired if damaged.

Vermeil, (a French term pronounced vermeil), is a technique that bonds or electroplates a layer on minimum 10K gold over a base of sterling silver. Better vermeil pieces are plated with 14K or higher. The gold can be as thin as 2.5 microns, so inexpensive vermeil does not wear well.

Gold-filled jewelry is at most 5 percent gold by total weight. Gold rolled, gold plate, and vermeil contain even smaller amounts of gold, and so unless you have a very large quantity, it’s not practical to attempt to recover the precious metal content.

And as for “gold tone” jewelry? Tempting words, but they describe something that contains no gold at all.

Excerpted from a piece by Jane Viator in Antiques Roadshow Insider, Vol. 9, Number 6, June 2009.