Assay Testing

Scratch Test
Is the testing of gold, either as ore, bullion, coin or jewellery, to determine its fineness or purity.

Originally done visually by scratching the gold on a touchstone, treating the trace with acid and comparing it against standard marks A method still widely used. A more accurate method is that of fire assay, a technique understood by the Egyptians, which is the principal chemical method used today.  

Fire Assaying Test

In fire assaying, or cupellation, a small sample of the gold under test is weighed on a special balance. This is placed with a quantity of lead in a small crucible or cupel made of bone ash, which is heated in a muffle furnace with a draught of air flowing over the cupel. The lead and any base metals are oxidized and absorbed into the cupel, while the gold and any silver remain as a small button. The silver is then dissolved out with nitric acid, leaving a pure gold ¥cornet', which can be weighed and the gold content calculated by comparing with the original weight of the sample.

Specific Gravity Assay Test

A third method of assaying, also known since antiquity although only accurately applied in modern times, involves Archimedes' principle. This depends on the fact that the specific gravity of gold is nearly twice that of silver and more than twice that of copper. Thus, if gold is debased with either of these metals, its specific gravity is progressively reduced and its gold content can be approximately calculated. It is not an accurate method for fineness determination. This method is used primarily by museums and numismatists in checking ancient coins from which samples for fire assay cannot be taken. Instrumental techniques such as inductively coupled plasma spectroscopy, glow discharge spectroscopy and X-ray fluorescence spectroscopy are now accepted methods for assaying with varying degrees of accuracy.

 All pure Egyptian gold and silver are Hallmarked once created……..

Hallmark

Hallmarks are used on gold and silver from many countries around the Globe. In Egypt all pure gold and silver classified as 900 purity or above should all have a Hallmark. The lowest grade of gold used in Egypt is 18 karat. There is no 9 or 14 Karat gold used in Egypt. The Pure grades of gold and silver that have a Hallmark to prove their authenticity of purity will be Hallmarks recognized all over the world by qualified people.

Gold or silver that are without a suitable Hallmark should be treated as "white metal" as there is no guarantee as to how much gold or silver an un-Hallmarked piece contains.

Sterling Silver contains as much or more silver than British coins. The word Sterling has been in use since the 1200’s to mean High Quality Silver.

Silver Items that are marked Sterling Silver, means the items contain at least 92.5% OF SILVER. Some jewellery maybe marked .925 rather than the word Sterling. Meaning .925 – 92.5% silver content.
 

Egypt’s Hallmarks are:

 
1906 – Present.
The Cat figure was replaced by the Lotus Flower in 1946

Common purity Hallmarks followed by the country Hallmark. These below are British and are an example only as Britain allows less than 900 Silver to be Hallmarked. Egypt uses Hallmark on silver of 900 or higher purity.