Jewellery articles are not worked on precious metal in its purest form. It is an alloy composed of precious metal and other metals. So, the fineness defines the purity of a precious metal.
For instance, when you purchase a piece of jewellery in SILVER with fineness 925, it means that the alloy contains 92,5 g silver and 7,5 g of other metals.
Or, when you get a piece of jewellery in GOLD with fineness 19.2 kt (karats), or 800%, it means that the alloy contains at least 80% gold and 20% of other metals (the well known portuguese gold).
In Portugal, the legal mark of the precious metals is given by the National Institute Currency (NIC) that confirms the precious metal fineness by placing a legal mark (punção) on each piece of jewellery, according to the legal criteria. The symbol varies according to the precious metal involved.
Check the symbols here.
In Portugal, a legal piece of jewellery has to have two marks:
- The manufacture’s mark (a unique identification);
- The NIC’s mark, which confirms the fineness of the precious metal.
Therefore, whenever you purchase a piece of jewellery in Portugal, make sure you get the right fineness.