Authenticating Gold and Diamonds
To test for gold, you have to first rub some metal off on a stone, then apply acid.
Placing the probe against the diamond lets you know what's real with a green light and a beep.
Was that wheat-colored pendant you almost bought at the estate sale last Saturday really made of gold? And is that sparkling, pea-sized stone on the ring that you inherited from your grandmother really a diamond? Those are the kinds of questions that people who bring jewelry to the ANTIQUES ROADSHOW often ask Barry Weber, an antique-jewelry expert who has been examining jewelry at the ROADSHOW for nine years. Time and again he confronts a tough question: Is my gold or diamond real—or just a cheap pretender?
How to find out if your gold or diamond is real—or just a cheap pretender
"Alchemists never did figure out how to turn metal into gold," says Barry, CEO of Edith Weber Associates in New York City, "but they've known how to test gold for centuries, and not much has changed." Before turning to alchemy, Barry suggests you examine your piece carefully with a jeweler's loupe for any stamped marks that will provide the answer. The U.S. government did not require gold manufacturers to stamp their jewelry to designate its gold content until the early 1900s. That's when it became common to see stamps for 10-karat, 14-karat, 18-karat, etc. But in older pieces these marks are often absent. Barry notes that laymen will also have a difficult time deciphering hallmarks on old or new European jewelry.
For these pieces, the gold test is the answer. "You've heard the expression, 'Give it the acid test,'" Barry says. "Well this is literally giving gold the acid test." The process begins by rubbing some of the metal from the jewelry against a slate (or sometimes a special piece of glass). "It scrapes off the gold like chalk on a board," Barry says, yet so little gold rubs off that it doesn't damage the jewelry.
Then, acid is poured on the metal residue that was rubbed onto the slate—not a procedure that Barry recommends you try at home. "It's dangerous," Barry says. "The acid can damage your clothing and your skin."
That's why Barry recommends you have a jeweler test your gold (if they do charge you, it will usually be only a nominal fee). If the metal rubbed onto the slate completely disappears under the acid, the piece is not gold. But if any metal remains, then it is gold, and the amount that's left can be measured to provide an indication of its fineness.
The science for testing diamonds was developed much more recently. Traditionally, jewelers would have to take gemology courses to learn how to identify real diamonds. "You had to go to school to learn how to use a microscope to look deep into a diamond to see if it was real," says Barry.
In the 1990s, though, a battery-operated probe was developed that can measure the speed of heat traveling through different types of stones. The pen-shaped device not only detects diamonds, it can distinguish natural diamonds from synthetic ones—a task that even diamond experts find challenging. If the diamond is real, the meter along the side the probe displays a green light and beeps, to make sure you get the point.
"They're not dangerous or difficult to use," Barry says of the diamond probes. "If you're out there at the Brimfield Fair or out hunting for jewelry at estate sales, this can tell you if you're looking at a real diamond. It's not rocket science, but it is science, and it's a wonderful tool to have here at ANTIQUES ROADSHOW to tell me quickly if a stone is real." You can buy the device for under $100, and Barry says you can find retailers of the probes by doing an Internet search for the phrase "diamond testing equipment."
Still, the device hasn't put Barry or any other jewelers out of business. "It's not going to tell the grade of your diamond," Barry notes. "You're still going to have to go to an appraiser to learn about a diamond's color, clarity and cut."
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