There are numerous precious metals. The most chosen solid metals used in jewelry making are Silver, Gold, and Platinum. When jewelry items are manufactured, the FTC (Federal Trade Commission) requires all items be stamped with a Quality Mark. This mark confirms the amount of precious metal used to make the piece.
QUALITY MARKS & MAKER'S MARKS
Hallmarks are letters, numbers, or symbols embedded somewhere on any jewelry item to identify it. It may be a maker's mark, quality mark, or even the gemstone carat weight. These marks are necessary for international trade.
Designers typically strike the metal with their insignia or laser engrave it. Criminals counterfeit these Hallmarks and sell fake designer goods into the market. You must be careful where you purchase your pieces from. Jewelry is beauty and art; but also an investment. Experience along with Jewelry Forensics is used to authenticate signature pieces.
QUALITY MARKS AND PATINAS
STERLING & FINE SILVER
Silver is a soft metal. Fine Silver is considered as any item comprised of 99.9% Silver. Sterling Silver is anything containing 92.5% Silver.
Because of the FTC, the item is stamped/ engraved using its pecentage amounts. In the case of Fine Silver it is stamped 999; Sterling Silver is stamped 925. You should be able to locate one of these stamps on any Silver item purchased.
Two typical patinas applied to Sterling Silver pieces are Oxidation and Black Rhodium.
Oxidation is a process where over time the Silver metal will tarnish; darken, or turn a grayish/ black in appearance. This process can be sped up using sulphur. If the process is not done right, the sulfur can turn your finger yellow, brown, or green. Pieces are "blackened" using this process. The black appearance also provides a great contrast in the crevasses of any Silver item.
The Black Rhodium process is also used to darken Silver. Unlike Oxidation, it is an electroplating process that applies a coat of Black Rhodium metal over the Silver. This process is also stable, but the Black Rhodium will wear off over time. Any jeweler should be able to reapply it.
Quality Marks & Electroplating
First, Gold is Gold. In other words, Gold cannot be any other color than Gold without the help of other alloys; mixed metals. Mixing Nickel and Palladium (white metals) with Gold gives us White Gold. Mixing Copper results in Rose Gold. As Gold tarnishes and loses its luster, it shows through more. White Gold will turn a dingy yellow. Yellow Gold will become orangy-Yellow, and Rose Gold will darken to an orangy-Red. Repolishing an item will return it to it's original luster, brilliance, and color.
In addition, Gold, like Silver, has it's own Quality Marks. Gold is stamped with one of five Quality Marks. Those marks are 417, 585, 750, 916, & 999. Just like Silver, those numbers correspond to the percentage of Gold in the item. For example, 417 marks the item as 41.7% Gold. 750 would mark the item as 75.0%. Gold is expressed in Karat Quality according to its pecentages. If 24 Karat Gold is Pure 100% Gold, you can divide the Quality Mark 10K into 24K and multiply by 100 to get the Gold's percentage when expressing it in Karat form.
75.0% Gold/ 100 = 0.75 x 24K = 18 Karat
10K/ 24K x 100 = 41.7% Gold
Using the 10K Gold percentage as an example, let's discuss how we get to White Gold since Gold is not White. Considering 10K is 41.7% Gold, mixing the other 58.3% with white metals like Nickel, Zinc, Palladium, and Platinum will displace the Gold color leaving the metal whiter.
Last, in order to completely whiten the metal and give it the look of Platinum, it is finished with White Rhodium. This Rhodium process is the same as the Black Rhodium process and will also wear off over time. Remember, Gold is soft, but Rhodium is hard. The higher the Karat Quality, the more Gold; the softer the piece. You don't normally think about it when it comes to wear, but just taking your ring off and setting it on the counter actually produces fine scratches that accumulate and beat away at the Rhodium Metal.
Platinum is the rarest of the three here; one of the strongest and most enduring metals in the precious metals family. Platium does tarnish. However, because Platinum is a white metal, it darkens to a metallic gray in appearance. Like Gold, Platinum can be polished to it's origianl state.
Quality Marks are represented as 850 for 85.0% Platinum, 900 for 90.0% Platinum, and 950 for 95.0% Platinum. The Quality Mark "PLAT" is regarded as 95.0% Platinum.
Next to Platinum, 14K White Gold would be a great option. Why? Think about it. At 95.0% Platinum, that is almost completely Platinum. A 14K White Gold piece will contain 58.3% Gold and the rest hard metal alloys. 14K White Gold is also eletroplated with Rhodium. Rhodium is harder than Platinum.