Gold Coin testing

How to correctly test gold coins.

For as long as gold has had any worth, there have been people who tried to make it themselves, and those who attempted to pass off other metals as gold by counterfeiting. 

There are counterfeits anyone can tell apart from the real thing, and then there are incredibly detailed clever counterfeits that, even today, can fool an expert. Counterfeit gold is everywhere from the smallest gold chain to the rarest coins in a collection.

Here are some of the ways gold coins have been tested in the past, and are now. You can be the judge of which tests we trust here at Almagrove!

 

Magnet test

Any magnet will not stick to gold – thought of course any gold mixed with other metals will often be magnetic. Worth remembering gold is not the only non-magnetic metal and a fake coin could well pass this test. Nowadays the magnetic test is done but only as an aside to further testing.

Size and Weight

Gold is one of the densest metals on the planet, and has physical properties that are very hard to replicate. Put simply in order to weight the correct amount fake coins would have to be wider or thicker. One exactly the correct size would be lighter. Knowing what your gold coins should weigh means it is easier to spot a fake.

Colour and shine

Gold is a soft metal that does not tarnish. It is a beautiful soft yellow colour and not very shiny. If your coin is too shiny, too yellow or has a reddish tinge then its not pure gold.
This is often combined with the Vinegar test – fill a glass bowl with white vinegar and allow gold to sit in it for about 15 minutes. Remove and rinse. Real gold will shine softly, fake gold will discolour.

The Ping test

Precious metals make a much higher pitched sound when struck than any base metal. Balancing the coin on your finger and tapping with another should cause a ringing sound. The difference between tapping a gold coin and one made of non-precious metal should be obvious.

Ceramic test

If you have an unglazed ceramic plate or a black jewellers stone, and firmly draw your gold coins across it, it would leave a gold mark. If it leaves a black mark it is fake. 

The bite test 

We really dont recommend this one!  but ‘back in the day’ gold was bitten as the softness of 24 carat gold would mean your teeth left a slight indent. And probably damage your teeth!

Stack test

On counterfeits the attention to detail is often lacking on the edge or relief. It may be higher, rougher,  or not as detailed as real coins of the same heritage. Stacking your test coin with other real ones of the same supposed age and denomination means this becomes quickly apparent. Real coins also stack neatly and stay stable, where as fakes will teeter and tumble over.

Nitric Acid test

Gold is resistant to oxidation and corrosion and not affected by acid. Applying acid will however permanent damage any coins not pure gold and this test should be done with caution! 

X-ray fluorescence analysis

This high tech method exposed coins or bullion bars to x-rays and the reflecting radiation is analysed. The disadvantage to this test is that if the real gold is merely a very thick coating the test may still fail to show what’s inside.

In-depth analysis via ultrasound

Testing by ultrasound goes much deeper then acid or X-rays. It works one the fact that different metals have different times that an ultrasounds needs to penetrate. Even excellent forgeries with base metal cores are detected. 

Cutting or drilling

Often the counterfeit icons are coated with thick gold and this allows them to pass most of the above tests. Jewellers and pawnbrokers still like to cut or drill into coins to allow them to test metal further down. Unfortunately this obviously damages the coins greatly plus devalues them as coins, and unless they are heading to be melted, most customers dont want that. 

In order to know for sure its gold,  the rule of thumb is to always associate with respected gold dealers and auction houses when adding gold coins or bullion to your collection. Once a counterfeit is verified, the coin is usually confiscated and destroyed with no recourse for the collector, taking it out of the counterfeit circulation.