Gold Purity Measurement

If you’ve shopped for gold jewelry or ornaments, you know how important it is to be certain of the gold you’re buying. 

So how do you measure gold purity?

Gold purity is measured in Karat. Karat is mostly classified into 10,14, 22, and 24 karats.

A piece of jewelry with 24 karats has 100 percent gold with no alloy.

But jewelry pieces with 24 karats are not common because 24 karat is very soft and delicate. Gold jewelry pieces in the market are usually between 10 karats and 22 karats.

Terminologies used in gold purity measurement

Gold Purity:

Gold purity is the gold-to-metal additive ratio.

Assay:

Assay refers to the test that helps determine metal content and quality.

Carat:

 Carat is a unit of weight used to measure precious stones. It is not Karat in North American English. One carat is equivalent to 200 grams.

Hallmark:

Hallmark refers to the symbol stamped on pieces of precious metals like gold and silver. It helps determine and certify the standard of purity of the metal.

Malleability:

Malleability refers to how easily a metal can be hammered to form various diverse shapes. The metal is usually hammered using compressive force. Malleable metals are those metals that can be easily hammered to a thin sheet.

Ductility:

Ductility refers to how easily a metal can be hammered. Unlike malleability, ductile metals are deformed using tensile force. Ductile metals can be stretched into thin wires easily.

Bullion:

Precious metals in their bulk, uncoined form are tagged bullion. For example, gold bars are referred to as bullion. It is expressed in mass and not value.

Troy weight:

 Troy weight is the system used in measuring gemstones and precious metals like gold and silver. A full troy pound is equivalent to 12 troy ounces and not the 16 avoirdupois ounces in a standard pound.

Troy ounce:

 Troy ounce is equal to 31.1034 grams. It is also equal to about 1.09714 avoirdupois ounces.

Millesimal fineness:

Millesimal fineness refers to the system that helps indicate the purity of precious material. Rather than Karat, millesimal fineness indicates purity by parts per thousand.

Karat:

Karat refers to the unit of measurement for gold fineness.

 

What is Karat?

Karats, known as carats outside of North America, are the numbers you can find on a piece of gold.

It is usually in the format of “xxK” or “xxKT” The numbers are usually stamped on gold and indicate the gold content in the jewelry piece or ornament.

Karat is also a measurement of the ratio of gold to other metals in a particular choice of jewelry. The other metals are usually silver, copper, palladium, and nickel in some rare cases.

Karats are usually measured on a scale of 0 to 24. High karat numbers refer to high gold content in the jewelry and low metal content. 24 karat is the purest gold you can purchase.

Karat vs. Carat: What’s the Difference?

Using Karat to measure gold purity

To measure a jewelry’s gold purity, you must first know the number of karats in that jewelry. Once you know the amount of Karat in a piece, you can easily calculate how pure the piece you’re looking at is.

To get gold purity, you will need to divide the number of your gold piece by the possible number of Karat that a gold piece can have.

For example, you purchase a piece of jewelry that is 10k gold. You’ll divide 10k by 24k, which is .416 or approximately .417. So your gold piece is 41.7% pure.

 

What is Fineness?

Fineness is another way you can use to measure gold purity. It is usually expressed in parts per thousand. So in fineness, a 24k jewelry will be expressed as 1000 parts out of 1000.

To calculate the fineness of a piece, you’ll need to divide the number of Karat of the piece by 24 and multiply by 1000.

So the reason why a 24k jewelry is expressed as 1000 parts out of 1000 is that 24÷24 × 1000 which is equal to a fineness of 1000.

Although 24k jewelry has a supposed fineness of 1000, it is said to have a fineness of .999 because every piece of gold has slight impurity, even the purest.

Tests to determine gold purity

It would help if you got your gold from reputable sources to save yourself the trouble of purchasing fake gold.

But if you want to confirm the purity of your gold, there are various tests you can carry out at home to determine gold purity.

These tests are:

Acid Test

The benefit of the acid test is that it harms artificial materials in your precious metals, so it can easily help you determine if your gold is counterfeit.

You can carry out a nitric acid test. Nitric acid does not affect the properties of pure gold, so it’s safe for your pieces. 

Make a small mark on your gold piece to penetrate the surface, and drop nitric acid on the mark you made.

Real gold won’t react to the acid keeping your gold in its original state. If your gold is counterfeit, the place you dropped nitric acid on will turn green.

Magnifying Glass Test

The magnifying glass test is one of the simplest tests to determine gold purity.

Once you have your magnifying glass and your precious metal, check for any of the following:

Discoloration:

Regardless of the environmental factors, your gold will stay in the same state. So if there’s any discoloration mark on your gold then it’s either fake gold or a gold-plated piece.

Shiny:

If you observe that your gold is extremely shiny then it’s fake. Real gold is not extremely shiny.

Color:

Real gold features a soft yellow color. Fake gold is usually shiny yellow, reddish, or a strange color.

Magnet Test

Another convenient method of testing for gold purity is using a magnet.

magnets do not attract pure gold, so there wouldn’t be any attraction if your gold is pure.

Magnets attract fake gold and various alloys that are posed as real gold.

Is gold magnetic?

Float Test

Genuine gold will sink into the water, and this is because of its high density of gold.

So to carry out the float test, you need to place your gold piece in water. If it is genuine, the gold will sink. On the other hand, fake gold items will float when placed in water. However, you cannot fully rely on the float test because some gold-plated or fake gold pieces are made with heavy materials and will sink in the water.

Other tests you can use to determine gold purity

There are some tools you can use to determine gold purity, and they are:

Electronic Tester

You can use an electronic tester to check if your item is pure gold. The reason why this works is because of the electronic conductivity of gold.

To test gold purity with an electronic tester, you need to apply a specific liquid to the surface of the gold item. After using the liquid, create a circuit between the electronic tester and the gold item. Next, apply an electronic charge and measure the resistance level.

If you carry out the test on a fake piece, the tester will indicate “not gold”, and if it is real gold, the tester will indicate the item’s purity.

XRF Spectrometer

The XRF spectrometer is one of the most accurate tools to identify real gold.

XRF (X-ray fluorescence) spectrometers can identify pure gold in a short amount of time. It is really expensive and is mostly used by gold processing factories.

The machine doesn’t only determine the gold purity of the item being tested, and it also measures all other materials that are used in making the piece. Hence, providing full information on the piece being inspected.

Some stamps on gold and their meaning

EPNS:

EPNS stands for Electroplated nickel silver, a silver plate. If you find this stamp on a gold piece, the item is worthless.

GF:

GF is like a gold plate. Items with the stamp have a minimum quality of 10K gold. The gold content is usually at least 1/20th of the weight of the piece.

375:

Gold items with this stamp are 9K or 37.5% pure. Some countries allow the marketing of this item as gold, but in the US, gold items must be a minimum of 9K.

417:

Gold items with this stamp are 10K or 41.7% pure. It is great for the jewelry market and for marking industrial machines.

585:

Gold items with this stamp are 14K or 58.5% pure.

Frequently Asked Questions About Gold Purity

Does High Karat mean High Quality?

High Karat indicates the amount of gold in a piece. The number of Karat in a piece does not necessarily translate into quality. Your best option is to determine what you need your gold piece for and which number of Karat works best.

What is a good purity for gold?

A 24K gold item is 100% pure gold without additional material. However, it is usually 99.9% pure because gold usually has slight impurity. 

What gold is best, 22Kor 24K?

If you’re making jewelry, 22K gold is the best bet because it has other materials. The presence of other materials in gold makes it stronger. Hence in this situation, 22K is best for jewelry. 

Is 22K gold the same as 916?

Yes, 916 gold is the same as 22K gold. 916 indicates the purity of gold in the item. Hence an item with the same 916 means 91.6 grams of pure gold. 916 is obtained by dividing 22 by 24.