ver also comes in various quality grades, measured by 1/1000 parts per gram. There are impurities that naturally occur in silver at the molecular level. These impurities consist of other metals - usually copper, but traces of other metals can also be found. These trace impurities are insignificant, and would be too costly to remove - so .999 silver is considered pure. .925 sterling is 92.5% silver and 7.5% copper.
Platinum - ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM). Platinum is a beautiful silvery-white metal, when pure, and is malleable and ductile. Platinum's natural white luster provides a rich backdrop for diamonds, but it's a metal that's just as elegant when used all by itself to create a piece of jewelry, either a simple polished item or a design with engraved motifs. Platinum looks stunning when combined with contrasting touches of 18K yellow gold. Platinum content is usually expressed as the amount of pure platinum the jewelry contains in parts per thousand. Jewelry that contains at least 950 parts per thousand of pure platinum may be marked or described as "Platinum"
Base Metals - In alchemy, a base metal was a common and inexpensive metal, as opposed to precious metals, mainly gold and silver. In chemistry, the term base metal is used informally to refer to a metal that oxidizes or corrodes relatively easily, and reacts variably with dilute hydrochloric acid. Examples include iron, nickel, lead and zinc. Copper is considered a base metal as it oxidizes relatively easily, although it does not react with HCl. Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modifies the properties of pure metals to produce desirable characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and luster. Alloys in use today are the alloys of iron (steel, stainless steel, cast iron, tool steel,alloy steel); the addition of silicon will produce cast irons, while the addition of chromium, nickel and molybdenum to carbon steels (more than 10%) results in stainless steels. Other significant metallic alloys are those of aluminium, titanium, copper and magnesium and bronze.
Bonding and Plating - There are different grades and methods of bonding precious metals to a less expensive base metal. Many jewelry items are made of either plated, bonded or filled metals. This is done to keep the cost of these items as low as possible.
- Filled Metals - have one or more layers of precious metal bonded to a base with heat and pressure. Filled materials are at least 1/20 precious metal by weight. Filled metal objects are marked with a quality stamp such as 12k GF or 14k GF.
- Flash or plate - These terms refer to the thinnest gold, silver, platinum or rhodium coating. There is no standard thickness.
- Electroplated - In this process, metals are electrolytically deposited on a base. These metals have a required minimum standard thickness - usually 15 - 25 mils (millionths of an inch). Heavy Gold Electroplate has a minimum thickness requirement of 100 mils to be stamped: (HGE).
- Clad - A composite metal containing two or more layers that have been bonded together. The bonding may have been accomplished by co-rolling, co-extrusion, welding, diffusion bonding, casting, heavy chemical deposition, or heavy electroplating. It is thought to be a good technique for coating as there seems to be an increase life-time of wearing part by 6-7.
- Gold, Platinum or Silver Filled - A layer of karat gold, platinum or silver is mechanically bonded to a base metal, usually brass or steel. Gold filled is marked with the gold percentage by weight and the karat value. If a piece of jewelry is marked 1/20 14K GF - 5% or 1/20th of the total weight is 14K gold.
- Vermeil - Gold plated over silver. Silver is the "base" metal. Typically 100 mils (millionths of an inch)must be the thickness of the gold plat