Our Expert Agrees: Suspicious marks and discolorations around the edges of the item are often telltale signs that the gold is fake. However, if the item is not 24k gold, which is considered pure gold, it may tarnish over time as the base metals are exposed to oxygen.
Genuine gold will stand up to your attempt to conduct a nitric acid test at home. Make a tiny mark on the piece of gold to penetrate the surface. Drop a small amount of liquid nitric acid on that scratch and wait for a chemical reaction. Fake gold will immediately turn green where the acid is.
Gold is a very soft metal, so scratching it with a hard object like ceramic will leave a golden or a yellowish streak. On the other hand, fake gold is often made of metals that are darker in color, so you'll see a dark streak instead.
The Ceramic Scratch Test
Take an unglazed ceramic plate or piece of tile and scrape a piece of gold across its surface. Real gold will leave a gold mark or trail. Other metals will leave a black trail.
Vinegar is very destructive, so when you apply the vinegar to a fake piece of gold, the vinegar will cause the jewelry to tarnish. Gold is a non-reactive metal, so real pieces of gold will not react to vinegar.
Out of all of the options, gold plated pieces are the most affordable. However, because there is a thin layer of gold applied to a base metal, gold plating over time will wear away or can flake off.
Plated gold's exterior coating will wear away over time since gold is soft and that layer is pretty thin. If you have been using any gold items for a while, inspect the edges and the parts that touch your skin or clothes. Seeing another color underneath means it's fake or plated.
While brass is not bright yellow, it's more dull than gold. However, gold is much shinier causing its golden color. Impurities can cause the shiny metallic luster that is characteristic of gold to fade. The purity of the gold determines the shine of ornaments.
Pure gold on its own cannot stick to a magnet. However, if you have an alloy of gold, then it could stick to a magnet. An example of a gold alloy that may stick to a magnet is gold with over 20% of its atoms replaced by iron. In very cold temperatures this alloy of gold may magnetize all on its own.
Pure gold is notated as 24K – this is the highest karat level for gold meaning it is 100% pure gold. 18K gold is 75% purity level, 14K is 58.3% purity level, and 10K is 41.7% purity level. As you can see, the higher the karat number, the more pure gold comprises the metal.
The Float Test
All you need is a cup (or bowl) of water and your gold item. Place your gold piece into the water. If it's genuine gold, then it will immediately sink to the bottom of the cup. Pure gold is heavy due to its high density – 19.32 g/ ml.
Both cause a chemical reaction that disintegrates the alloys in the jewelry over time. (Nearly all gold jewelry is alloyed, because pure gold is too soft on its own.) One study showed that when a 14K white gold ring was placed in common household bleach for 36 hours, the ring completely disintegrated!
Heat your gold jewelry with the lighter.
Watch it closely for any changes in color. Fake gold will get darker, while pure gold will do the opposite: it will get brighter the hotter it gets. The brighter your jewelry gets, you can rest assured you have real gold.
In conclusion, it is not advisable to wear 18K gold-plated jewelry in the shower or while swimming. Exposure to water, soap, shampoo, hot water, steam, moisture, and humidity can pose risks of damage to the delicate gold plating.