Precious Metals
HALLMARKS
The precious metals participating in the wealth of a country, the state thus established a control and rules guaranteeing the value of processed products like jewelry.
Precious metals, gold, silver and platinum, are never used pure, they are allied to other less noble metals such as iron, copper, nickel.
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A hallmark is a guarantee of the precious metal content of the item being bought.
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For French country, Date of the law of 19 brumaire year VI (November 9 1797).
UK Hallmarks : Gold, silver, platinum and palladium items sold in the UK have to be hallmarked.
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The titer (mass fraction) of a precious metal alloy is expressed in thousandths.
If a title jewel 750/1000 (can be written 75), it means that it contains 3/4 of gold by mass.
No negative tolerance of title allowed.
As well as the Assay Office hallmark, there is the Sponsor's Mark (or the company where the item was made), and the Finesse Mark, which tells you the precious metal content of the item.
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The carat, which is often used as a non-legal unit, is defined as 1/24 of the total mass: 24 carats = pure gold, 18 carats = 750/1000. (Some jewelers write 18 K for 18 carats)
Gold is naturally yellow, but too malleable (say the goldsmiths). Metals will be added to give it superior mechanical characteristics or different shades. Red Gold : Gold + 25% Copper ; Grey or White Gold : Gold + Nickel or Palladium or Cuprozinc ; Yellow Gold : Gold + 12.5% Silver + 12.5% Copper ; Pink Gold : 9% Silver + 16% Copper Other shades exist, such as the alloy of 'green' gold (gold + silver), gold alloy 'blue' (gold + iron or cobalt), gold alloy 'violet' + Aluminum) |
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The silver is not used pure, other metals (often copper) are incorporated to form alloys, defined by their title.
Only certain securities are authorized and guaranteed. The so-called 'massive' silver is only 925. |
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Like the other precious metals, platinum is alloyed with palladium, rhodium, ruthenium, osmium or iridium.
The iridium associated with platinum is counted as platinum. |
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