Precious Metals


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.

A hallmark is a guarantee of the precious metal content of the item being bought.
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.
Jewelry Hallmark Karat

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.

jewerly hallmark

In the UK there are four Assay Offices, each with their own hallmark , London, Birmingham, Sheffield and Edinburgh.

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.


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)


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.

punch hallmark


Like the other precious metals, platinum is alloyed with palladium, rhodium, ruthenium, osmium or iridium.

The iridium associated with platinum is counted as platinum.


Various information

A second punch, specific to the Owner, is also affixed to the jewel.

- Its geometric shape is diamond-shaped for a French or oval manufacture if it is foreign, a square indicates a gold-plated jewel.

- The vermeil is a 925 silver substrate plated with at least 5 micrometers of gold at 750

- The gold-plated must have at least 3 micrometers thick gold.

- The quality of 'end' as 'fine gold' applies to securities of 999.

- If the state guarantees the title of the metal of a jewel, it levies a tax.
The presence of the punch is also a guarantee of payment of taxes.
All the decrees and laws in force govern the general tax code.

- The regulations impose on professionals (manufacturers, dealers, auctioneers))
The holding of a 'police book' for the purchase, sale, receipt and delivery of articles of precious metal.

1st title : 950 ; 2nd title : 900 ; 3rd title : Small guarantee uncertain origin ; Gold Alloy (75 % & or ? 50 %) ; Silver Alloy (silver & 50 %) ; Mixed alloy (gold and silver)

Sites to consult

Jewelry Hallmark Karat


Precious Metals Assay & Hallmark Center
The Gem and Jewelry Institute of Thailand
(Public Organization) ITF-Tower Building.
4th Floor, Silom Road, Suriyawong
Bangrak, Bangkok 10500,

Tel: +66 2634 4999 ext. 421
Fax: +66 2634 4970
Jewelry Hallmark Karat


Mon - Fri: 09:30 - 17:00
Closed on Thai government public holidays



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