Pure (fine) gold is yellow. Gold (Au) is the most malleable and ductile of all metals. It is chemically inactive; in other words, it is not affected by oxygen, sulfur, or acids; however it can be dissolved in a mixture of nitric acid and sulfuric acid. Gold is used for many purposes, jewelry, dental, coins, decorative. Pure gold is soft and is alloyed with other metals to resist wear.
When gold is alloyed with other metals such as silver, copper, nickel, or platinum the resultant color that is produced will vary. For example, mix gold with platinum, or nickel, will produce white gold. Green gold is made by mixing gold with silver and copper. Red gold or rose gold is produced by adding a little more copper than silver. Gold mixed with silver, copper, and zinc produces yellow gold; the amount of pure gold is measured in units of karats. 24 karat is pure gold, 18 karat is 75% pure gold (18/24), 14 karat is 58.3% (14/24) pure gold, and 10 karat is 41.7% (10/24) pure gold. Most jewelry pieces are stamped to indicate its purity, for example, 14kt, or 14K, or 583 (jewelry made in Europe will be stamped in this manner).
The following is a list of melting points for pure gold and alloyed gold:
24 karat pure gold 1945°F
18 karat white gold 1730°F
18 karat yellow gold 1700°F
14 karat white gold 1825°F
14 karat yellow gold 1615°F
10 karat yellow gold 1665°F
Gold filled metal is used often as an inexpensive alternative to gold. It is gold layered onto a base metal, like brass or steel. There is 14 karat or 12 karat gold filled metal. A jewelry piece will be marked for example, 14/20 gold-filled, 1/20th (or 5%) of the total weight of the metal is 14-karat gold.
Another gold product often used is Vermeil (pronounced: Vehr-MAY). Vermeil is a product that is made from a base of sterling silver that is coated or plated on its surfaces with gold of at least 14 kt and at least 2.5 microns thick (100/1,000,000 inch). Vermeil is also known as silver gilt, gold Vermeil, and sometimes as silver gilded.
A gold plated piece means that a very thin layer (1/100,000 of an inch) of 10 karat gold is layered onto base metal like brass or steel. Gold filled is better quality but more expensive than gold plated. Usually, a gold plated item will tarnish, and gold filled does not.
Troy ounce is the unit of weight traditionally used for precious metals. Silver, gold and platinum are precious metals. Troy ounce is equal to about 1.1 ordinary ounces. The word ounce when applied to precious metals refers to a troy ounce. Many people don't know this so when they look at the precious metal market quotes they think on a per ounce basis; it is really a troy ounce. 1 troy ounce = 1.1 ounces.
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