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To Assay :- A metal (such as silver or gold) it is subject to chemical analysis, to determine the amount of alloy. The most accurate and widely used method, with an accuracy of 2-3 parts per ten thousand (0.02%), is the Fire Assay (Cupellation) method, This involves taking a small scraping form the article, typically about 250 milligramme's, weighing it accurately, wrapping it in lead foil with some added silver, cupelling it in a furnace at about 1100 C to remove all base metals and then placing the resulting gold-silver alloy button in nitric acid to dissolve out the silver (known as 'parting') and re-weighing the resulting pure gold.
This is the standard reference technique used by the national Assay laboratories worldwide for Hallmarking and is covered in the International Standard, ISO 11426:1993
All items :- Supplied by me are hallmarked as a matter of course to protect your interests unless it is produced in Palladium which is a very special product and would carry specified certification.
In the U.K.:- 9 carat is very popular it is hardwearing and used for Bangles, Bracelets and Chains, however 18 carat is also used for most applications but does command a higher price because it is twice as pure.
You can see why the assay office charge so much for their services. |