Precious Metals

All lasting pieces of jewellery are manufactured from either platinum, gold or sterling silver. The main reason for this is that these metals are all hard wearing and in the case of pure gold and platinum, do not corrode with general exposure. All metal corrodes with wear and tear, but these three have stood the test of time and have come out as the most suitable for jewellery. All jewellery is also made of alloyed metal. This means that the metal is not used in its purest form, but mixed with other metals, such as palladium, copper, zinc and tin, to give it other properties that the pure form of the metal does not possess naturally. For this reason jewellery is hallmarked, or stamped, with a mark that distinguishes the alloy and will tell you what the piece is made of. The following hallmarks are the most commonly used in South African jewellery:

Sterling silver, S/silver, 925 – These marks on jewellery tells you that the piece is made of Sterling Silver. This means that the object consists of 92,5% pure silver and 7,5% of other metal. The most common metal used to alloy silver is copper, but palladium is also used. Why do we alloy pure silver? Because silver in its pure form is very soft and will be unsuitable to wear, as the object will loose its original form far to quickly. When pure, silver is as bright white metal.

9ct, 9k, 375 – These tell you that the object is made of 9ct gold. Whether white, red or yellow, if the jewellery is marked with this stamp, it means that it contains 37,5% pure gold and 62,5% other metals. The other metal added to the gold, gives it its colour as well as other properties that makes the metal more hard wearing. (Gold, in its natural pure form, is yellow.)

18ct, 18k, 750 – As in the previous two cases, these marks will help to identify the jewellery piece. In this instance it tells you that it's made of 18ct gold. In this instance it tells you that its made of 18ct gold, which consists out of 75% pure gold and 25% other metals. Again, the other metals will give the gold its colour and other properties that may be needed to produce a certain piece.

960, Plat, Pt – These marks are used to identify jewellery manufactured from platinum. Platinum is sometimes used in its pure form or alloyed (mixed) down to 96% pure to give it a better workability. Platinum has a slight gray undertone in its natural unalloyed state.

Nearly all white gold jewellery is rhodium plated. This means that a thin layer of rhodium (a metal that is like platinum, just bright white in colour) is deposited onto the gold item using a technique called electro–plating. It is done to give the piece a bright white appearance as well as to give it some protection, as rhodium is a harder metal than gold or silver.

Luxus - Designing and Manufacturing Jewellers