Pure 24K gold is soft. it is usually alloyed with base metals for use in jewelry by alternating its properties.
Combining gold with base metals in common. A lower grade of gold or copper is common place. Using copper as an alloy will turn the gold a redder color.
Eighteen carat gold containing 25% copper is found in antique and Russian jewelry and has a distinct, though not dominant, copper cast, creating rose gold. Fourteen carat gold-copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police, as well as other, badges. Blue gold can be made by alloying with iron and purple gold can be made by alloying with aluminum, although rarely done except in specialized jewelry.
Blue gold is more brittle and therefore more difficult to work with when making jewelry. Fourteen and eighteen carat gold alloys with silver alone appear greenish-yellow and are referred to as green gold.
White gold alloys can be made with palladium or nickel. White 18 carat gold containing 17.3% nickel, 5.5% zinc and 2.2% copper is silver in appearance. Nickel is toxic, however, and its release from nickel white gold is controlled by legislation in Europe. Alternative white gold alloys are available based on palladium, silver and other white metals, but the palladium alloys are more expensive than those using nickel.
High-carat white gold alloys are far more resistant to corrosion than are either pure silver or sterling silver. The Japanese craft of Mokume-gane exploits the color contrasts between laminated colored gold alloys to produce decorative wood-grain effects.
When buying gold it is a good practice to verify that it is real and not fake!
1 Wear your gold jewelry for at least a day. If you notice a mark or discoloration on your skin where you were wearing the jewelry, it is most likely fake.
2 Lightly stick a pin into your piece of gold jewelry. If it is real gold, the pin will not break because gold is a soft metal and fakes are not.
3 Place your gold jewelry near a magnet. Real gold is not magnetic; if your jewelry pulls toward the magnet, it is fake.
4 Clean your gold piece with a jewelry-cleaning cloth three times. If your gold is fake, the cloth will remove the gold color off the jewelry.
5 Take your gold jewelry to a local jewelry store if you are still unsure. They can take an X-ray and run a gold test to let you know for certain.
Real gold is a light shade of gold and not very shiny, so take a long look at gold jewelry before you buy it.
Just because a piece of gold jewelry is stamped with "14k" does not make it so; do not assume it is real without checking.