Much of our jewellery is designed using Cad-cam software. With this software we can determine how heavy a piece of jewellery is by using specific gravity. Below you can see that there is a considerable difference between the specific gravity of silver and gold. Gold has a specific gravity of 19.3 in its pure form and thus feels heavier than pure silver which has a specific gravity of 10.5. The specific gravity can also be used to test whether something is silver or gold.
An example of this is the Archimedes water test. Archimedes was a Greek scientist in the 3rd century BC. King Hiero II asked him to test a gold crown for authenticity. He of course couldn’t damage the crown.. After pondering for a long time he thought of a solution for this problem in his bathtub. Enthusiastically he jumped out of his tub and ran through the streets naked screaming ‘Eureka, eureka’. What he had discovered is what we now recognise as Archimedes' principle: Volume = Mass / density, which means that:
An object submerged in a fluid or gas experiences an upward force equal to the weight of the fluid or gas it displaces.
Therefore, the difference in weight is equal to the weight of the water displaced. By dividing this weight by the density of water (1 kg per cubic decimetre), we find the volume of the object. Multiply this volume by the density of gold to calculate the true weight of the crown. In this case, it turned out to be a silver-gilded crown.
Pure gold | 19.3 |
---|---|
22 carat yellow gold | 16.5 |
18 carat yellow gold | 15.4 |
18 carat red gold | 15.1 |
18 carat white gold | 14.8 |
14 carat yellow gold | 13.7 |
14 carat red gold | 13.1 |
14 carat warm yellow gold | 13.4 |
14 carat rose gold | 13.3 |
14 carat white gold | 12.8 |
9 carat yellow gold | 11.1 |
9 carat white gold | 10.7 |
Pure silver | 10.5 |
Silver 925 | 10.3 |
Silver 835 | 10.2 |