There are four primary precious metals - gold, silver, platinum and palladium. The most expensive metal is Rhodium, a silvery coloured metal used principally for its reflective properties.
Gold for jewellery use comes in 5 main types or fineness, determined by the proportion of pure gold.
9 carat - 37.5% gold
14 carat - 56% gold
18 carat - 75% gold
22 carat - 91.7% gold
24 carat or pure 100% gold.
In addition jewellers use gold plating, which is a base metal coated in gold via electrolysis. Gold vermeil, whilst similar to gold plating, has some key differences that make it distinctive. Vermeil is a technique originating in the 19th century, where gold was applied to sterling silver. Gold vermeil is also made through the gold plating technique but requires a thicker layer of gold. In this case, the gold layer must be above 2.5 microns. Another form is gold fill, a term used to describe an amalgam of gold mixed with brass or bronze. This is used by jewellers as an economical substitue for gold as it is highly durable, the colour will not fade/wear and costs far less than gold on its own.
How does gold plating and gold vermeil compare? Whilst gold plating can take place on any metal, from copper to brass, gold vermeil has to be on sterling silver. The second key difference is in the thickness of the gold layer. Gold plating has a minimum thickness of 0.5 microns, Gold vermeil has to be a thickness of at least 2.5 microns. When it comes to gold vermeil vs gold plated, gold vermeil is at a minimum 5 times thicker than gold plating.
Durability - due to its added thickness gold vermeil is far more durable than gold plating. Combining both affordability and quality.
Silver comes in two principal forms, silver plate and sterling silver. Silver plate, like gold plate, is formed by dipping a base metal into a solution for electrolysis, the result being a thin layer of silver.
Solid silver comes in three forms, sterling (92.5% pure), britannia (95.8% pure) and fine, or pure, silver. Since silver is a relatively soft metal jewellers tend to use only sterling silver, often described as 925 silver.