How to Test for Gold Purity


There are three main ways that your gold items can be “tested” to find the true percentage of actual gold that they contain. The hallmarks that you find on your gold are for the most part universally accepted, but they may not always be 100% accurate. Although variations in a gold item’s hallmark and the actual amount of pure gold it contains are typically very slight, they are somewhat common. And, although fairly rare, but not completely uncommon there are instances of gold items having “counterfeit” hallmarks (especially as the value of gold continues to rise). Depending on how much gold you have to sell, or perhaps if you have some gold items that have no identifying hallmarks as to their gold content, this information can be very helpful in identifying the true gold content of your items and therefore the overall value of your gold.

How to test for Gold:

The Acid Test

The easiest and cheapest (and therefore most commonly used) of these three tests is called an “acid test.” The traditional acid test for gold consists of scratching the gold item on a test stone (leaving a streak from the item on the stone) and then placing a small drop of a strong acid, (typically nitric acid) onto the streak. The test can also be done by placing a small drop of the acid directly onto the surface of the item being tested. This is usually only done with “scrap” items though because it will typically discolor the item where the acid comes into contact with it. Base metals fizz or bubble (and typically turn a bright green color) when they come into contact with the acid, while precious metals are unaffected. The acid test is thus decisive, immediate, cheap, and simple.


Gold acid test kits are inexpensive and can be purchased easily online or at local shops for as little as $10.00. A full kit will typically consist of at least 4 bottles of different strengths of acid (to identify the different karat value of your gold 10k, 14k, 18k, and 22k), a pair of gloves (for safety), a test stone, a file, and instructions on the proper use of the kit.

2The acid test is referred to as a “scratch test” when it incorporates into it what are called “test needles.” The test needles are simply a way of narrowing down a little bit more accurately by comparing the color that your gold item changes to the color that the test needles make when tested side by side. But because the test needles are simply small samples of real gold in different karat values, they are also fairly expensive. For the most part this is considered to be an “unnecessary” addition to the test.

It is important to note that while an acid test is in fact cheap, easy, and when done correctly a pretty accurate test, it does have a couple of downsides to it. The first is that an acid test requires that you scratch or place acid directly onto the item that you are testing (which can cause a slight discoloration where the acid comes into contact with the item). The second is that to be certain an item is “solid” gold and not simply gold plated or gold filled it requires that you place a fairly deep scratch or file mark in the gold item that you want to test. If your item(s) have a value beyond just their melt or “scrap value” (i.e. nice jewelry pieces, collectable coins, etc.) then I would not recommend using an acid test to find the purity of the item! It is probably going to be in your best interest to use one of the other two methods of testing gold purity instead.

Example video of how an acid test is done.

Electronic Gold Testers

Electronic gold testers come in a variety of different sizes and models but are typically small handheld style devises that are easily transported. They range in price from around $75.00 all the way up to around $900.00. Electronic gold testers detect gold and determine the purity of it by using an electrical conductivity test. Electrical conductivity is a physical property that indicates how well 3a given material conducts electricity. As you may be aware, gold is a very good conductor of electricity. The ability to conduct electricity is unique to different elements much as fingerprints are unique to different people. Electronic gold testers can detect when gold is present and how pure it is by evaluating the current that is passed through the item that you are testing. It requires that you use a special kind of liquid or gel (usually provided with the tester) to create a circuit between the gold tester and the piece of gold that you are testing. Electronic gold testers are considered by most gold dealers to be safe and accurate, but they do require some practice and careful cleaning to ensure continued accuracy. If the gel is not cleaned out of the probe in which it is placed everyday, clogging can occur. This however is only an issue when improper cleaning techniques are utilized. Because of the sensitivity of electronic gold testers, it is possible to get a “false” reading from one. Because of this there is some debate as to which is more accurate, the acid test or electronic test. The most important thing for you to know and keep in mind when using one (or dealing with someone who is using one) is that they are very sensitive and can give a “false” reading. If someone tests your gold that is let’s say for example hallmarked 14k and they say it’s only 12k because that’s what the electronic gold tester is reading, BEWARE! As I mentioned in the beginning of this section, it is actually quite common to find variations between hallmarks on gold and the actual REAL content of gold in the item, but again, it is most often fairly slight (plus or minus one karat). If any test tells you that your item is more or less than one karat of what it is hallmarked it is a good idea to get a “second opinion” by confirming the results with a different tester and/or a different type of test. DON’T get fooled or ripped-off because someone doesn’t know how to clean or use their electronic gold tester properly!

Example video of how an electronic gold test is done.

X-Ray Fluorescent Spectrometer

These machines are considered to be the most accurate way to determine the content of gold in any item; coins, jewelry, bullion, etc. without actually destroying the item. X-ray fluorescent spectrometers (commonly abbreviated and referred to as XRF) also come in various models and sizes from handheld to about the size of a standard desktop copier/printer. Below are pictures of two commonly used models that you might see a local gold buyer or gold assayer use at their place of business. These models typically cost between $13,000 and $16,000, but this can vary greatly depending on the specific manufacturer and model (some costing as much as $40,000 or more).

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The test does not require that your gold item be scratched, exposed to acid, or damaged in any way. XRF works by sending a very fine beam of x-rays at the item being tested which excites the molecules in that item. This moves the item being tested to a higher energy state, then as the item relaxes back to its normal energy state it emits a very small amount of radiation. The radiation emitted is done so at a very unique and characteristic frequency (again, much like that of a fingerprint) which the XRF machine detects and reads, sending the results to an attached computer that uses specially designed software which works in conjunction with the XRF machine. It is then able to tell you very precisely, typically within an error ratio of only 0.05% (and in some machines even less) what the item is made of! Now THAT is the kind accuracy you should be looking for when determining the value of your gold! The test typically takes from around 5 seconds to about a minute and a half (depending on the make and model of the machine being used).

Example video of how an XRF test is done.