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Friday, 16.11.2018, 18:32

Evriviadis Kosmimata

Precious Metal


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Gold

Gold is one of the worlds most widely deposited metals although it is always found in low concentrations.

Gold is a soft bright, yellow metal that occurs naturally and was formed millions of years ago by massive pressures and movements deep in the earths crusts. As gold is naturally a soft metal it must be mixed, or alloyed, with other elements to strengthen it.

The earliest discoveries of gold were probably in the river basins of Africa and Asia, and among the first underground mining was undertaken by the Egyptian mines on the Red Sea coast.

As the rocks cooled with the earths crust, so gold was trapped. Where these deposits were exposed to the elements the rock gradually wore away, leaving the gold particles free to settle by their own weight. These gold bearing gravels were often submerged by layers of lighter rock and soil debris called eluvium.

Once this layer is reached, the gold bearing layer can be washed in the prospectors pan or similar apparatus to free the gold.

Where is gold jewellery made?

The earliest known jewellery dates from the Sumer civilisation, which inhabited what is now Southern Iraq, around 3000BC. In the Egyptian tomb of King Tutankhamun, who dies in 1352 BC, some early examples of chain making and alloying were found. Since then Italy moved to the forefront of the gold jewellery industry. It has become the jewellery manufacturer to the world, using over 400 tons of gold annually.

Different shades of gold

The different elements that are alloyed to give gold it's strength, determine the finished colour. While yellow is it's natural colour, other tones are achieved by blending with other alloys. Gold alloys are usually a mixture of silver, copper and zinc and the amounts can be varied to affect the final colour.

Yellow Gold = Copper + Silver + Pure Gold
White Gold = Nickel (Palladium) + Zinc + Copper + Pure Gold
Green Gold = Silver + Copper +Zinc + Pure Gold
Rose Gold = Copper + Pure Gold

What do the different caratages mean?

The proportion of gold in jewellery is measured on the carat scale. Pure Gold is designated 24 carat, which compares with the fineness by which gold is defined.

Caratages

The carat preferences vary across the world. In Europe 18 and 14 carat are most widely used, although 9 carat is popular in Britain. Portugal has a unique designation of 19.2 carats. In the USA 14 carat predominates with some 10 carat. In the Middle East, India and South East Asia jewellery is traditionally 22 carat (sometimes even 23 carat). In China and Hong Kong "chuk kam", gold of almost 24 carat, is popular.

The carat code on the hallmark means the amount of gold an item of jewellery contains. The higher the carat value the greater the proportion of gold it contains e.g.. 9 carat gold is an alloy of 9 parts gold and 15 parts other metals.

The table below shows the purity and value shown as hallmark for the various carat value:

Carat Value % Purity Shown on Hallmark Mix of Gold to Alloy
9 Carat 37.50 375 9 to 15
14 Carat

58.50

585 14 to 10
18 Carat 750 750 18 to 6
22 Carat 91.66 916 22 to 2
24 Carat 99.99 999  

Hallmarking

Hallmarking began in England in 1300 and is the oldest form of consumer protection. The series of symbols that make up the hallmark are a guarantee of authenticity.

All items must be hallmarked unless they weigh less than 1 gram or 2 grams for a pair of earrings.

The hallmark consists of up to four symbols:

1. The sponsors mark.

This symbol, normally the initials of the designer or the company is chosen by the manufacturer and is stuck onto every piece of gold jewellery they make.

2. The quality Mark

This is the certificate of carat quality showing how much gold a piece of jewellery contains. It is represented by the symbol of the crown followed by numbers e.g. 375 is 37.5% pure gold or 9 carat as it is more commonly known.

3. The Assay Office Mark

In Britain there are four Assay Offices and each one has it's own symbol. Birmingham has an anchor, Sheffield has a rose, Edinburgh a castle and London a Leopards head.

4. The Date Letter.

This is a letter showing the year when the item was hallmarked e.g. 1996 was a W and the year 2001 was a B.

Under the Hallmarking Act 1973 (amended in 1999) gold, silver and platinum sold must be hallmarked at an Assay Office if the items are over a certain weight:

Gold if over 1 gram (therefore 2 grams for a pair of earrings).

Silver is over 7.78 grams.

Platinum if over 0.5 grams.

Under the law a hallmarked piece of metal must include the sponsors (manufacturers) mark, the fineness or the metal and the Assay Office where it was hallmarked. There are also other voluntary marks that can be made such as the year of hallmarking and commemorative marks (e.g. to celebrate the new Millennium or Golden Jubilee in 200 and 2002 respectively)The sponsors mark is generally about 2, 3 or 4 letter stamp e.g. G A or M S T.

The fineness is the purity of the metal or the parts per thousand. For example 18 carat gold is stamped 750 which is 750 parts per 1000 or 75% or 18 carats out of a maximum of 24.

Gold Fineness:


9 Carat
14 Carat 18 Carat 22 Carat   near 24 Carat


Silver Fineness:

  Sterling Britannia  


Platinum Fineness:

       


There are now 4 UK Assay offices each having their own distinctive mark.

Birmingham Edinburgh London Sheffield


There are many other marks that could be on an item of jewellery including optional marks, commemorative marks and valid Assay marks from Austria, Czech Republic, Denmark, Finland, Ireland, Netherlands, Norway, Portugal, Sweden & Switzerland.

For more information on hallmarking and the Assay offices click on one of the Assay marks about or visit the British Hallmarking Council.

Titanium

Titanium, the mineral that creates the lustrous metal was not discovered by a scientist as one might expect but by a vicar in Cornwall in 1791.

Reverend William Gregor, who was interested in minerals, recognised the presence of a new element in menachanite, a mineral named after Menaccan, a small village in Cornwall. Titanium is the 9th most common element found in the earths crust but also in meteorites, the sun, lunar rocks and even the stars. Closer to home, we all carry a low quantity of titanium in our bodies although it has no biological function.

Although the titanium mineral is found in abundance, pure titanium is not found naturally. In 1910, Matthew Hunter heated TiC14 with sodium in a steel bomb at 700-800 centigrade and created the spectacular metal we know today as titanium.

Titanium is as strong as steel but much lighter, twice as strong as aluminum and almost as resistant to corrosion as platinum. These qualities make titanium a popular choice to be mixed with other metals to produce alloys used widely in the aerospace and marine craft industries and a host of other projects.

Silver

It's working qualities are similar to gold but can achieve the most brilliant polish of any metal.
To make it durable it is alloyed with copper.

In many countries Sterling Silver is 92.5% Silver and 7.5% copper and has been the standard for jewellery since the 14th century.

Silver has always been held in high esteem and displayed as a status symbol since it was mined in approximately 4000BC in Asia Minor. In earliest Egyptian records, it was considered more precious than gold.

Throughout history wearing silver jewellery was often a social privilege and reserved for the upper classes.

It was the industrial revolution, through mass manufacturing, which finally made jewellery available to the general population.

Mexico is the largest producer of silver in the world. Zacatecas State in Northern Mexico is the heart of the silver belt. Peru is the worlds second largest silver producing country.

All silver articles over the minimum weight of 7.78 grams must be hallmarked. Sterling silver is 925 parts per thousand of silver and 75 parts base metal (usually copper).
 
 
 

 
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