One of the most likely reasons why gold turns black is all due to metallic abrasion, or low-quality plating as well as corrosion.
Gold itself does not corrode, but its primary alloys of silver or copper will do so, forming very dark chemical compounds under moist or wet conditions. When you sweat, fats and fatty acids released can cause corrosion of gold, especially when exposed to warmth and air.
No, gold does not react when exposed to sunlight. In other words, authentic gold jewelry will not tarnish or lose its golden shine. If your item starts to change color or lose its luster, it's probably counterfeit.
Although pure gold itself is highly resistant to tarnish, gold alloys, which are commonly used in jewelry for increased durability, can still be susceptible. Gold tarnish typically occurs when the metal reacts with substances like sulfur, oxygen, or various chemicals present in the environment.
Remove tarnish by using a soft cloth to clean your jewelry with a solution of warm water and a small amount of mild soap, which is any soap that is safe for repeated contact with skin and is free from harsh chemicals or detergents (e.g., phosphates, ammonia, bleach). Be sure to thoroughly dry your jewelry afterwards.
Dish soap
Pour about 3 drops of a mild dish soap into a bowl of warm water (you could also follow the rule of 1 drop per half glass of warm water). Stir to mix and then, place the gold jewellery in the solution for about 5-7 minutes depending on how tarnished it is.
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.
Will gold turn black when you burn it with a lighter? The gold will not turn black when you burn it with a lighter. However, if your piece of gold jewelry turns black when you burn it with a lighter, it is most likely fake.
There is gold that has been blackened, however. According to Calla Gold, a jeweler located in Santa Barbara, there are four ways gold can appear black: Oxidation. Special acids when applied to the surface of gold cause it to darken or “oxidize.”
Elements such as sulphur and chlorine react with the other metals in the gold jewelry, causing it to corrode and turn black, thus blackening the skin underneath.
Toothpaste and an old toothbrush or Q-tip.
Squeeze a small amount of toothpaste on to your tarnished piece of jewelry and smudge it with your finger. Once the jewelry has a thin coating, brush clean — working into the crevices — with the toothbrush.
A number of factors can cause silver chains to become tarnished including perfumes and body lotions but also sweat, exposure to air and even sunlight. Over time, any sterling silver jewellery exposed to air will tarnish.
Real gold does not change color. If you observe discolored gold, then your gold jewelry is not real. You can also test it by applying droplets of vinegar or putting your gold jewelry underwater to see if it changes its color. Observe any tarnishes or damages that might be caused due to time.
Scratch test.
If you cut deep enough that you expose underlying metal, you can assume that it is plated. If it appears to be made of a uniform composition throughout, then it is probably solid gold.
9ct gold (37.5% purity)
While pure yellow gold does not tarnish and will retain its original colour forever, the strong presence of alloys (the metals that make up 62.5 percent of 9ct gold) in 9ct gold are susceptible to discolouration.
Gold itself does not corrode, but its primary alloys of silver or copper will do so (forming very dark chemical compounds) under moist or wet conditions. When someone perspires, fats and fatty acids released can cause corrosion of 14 karat gold, especially when exposed to warmth and air.
The truth is, ALL fashion jewelry necklaces, earrings or bracelets are capable of tarnishing - and some faster than others. Why? It's simple - over time, your jewelry comes in contact with moisture, acids, oils and air. They react with the metal in the jewelry, causing it to eventually wear down and tarnish.
Understanding the Causes of Black Marks on Jewelry
The most common culprits are oxidation and tarnishing. Oxidation occurs when metal comes into contact with air, while tarnishing is a chemical reaction between the metal and substances like moisture, chemicals, or even our skin's natural oils.