PURIX
AI characterWhy does the colour of gold change?
Jewellery gold is usually not pure; other metals are mixed into pure 24 karat gold. This mixture makes gold more durable and can also change its colour.1
What sets the colour is the type of metal mixed in. White gold is made by mixing pure gold with white metals such as palladium or silver, and it is usually plated with rhodium. The colour of rose gold comes from copper. Unusual colours such as blue, purple or black are obtained with oxide or patina layers on the surface of the alloy.1
Same colour, different karat
Colour does not tell you how much gold is in the alloy. In the World Gold Council’s table, yellow gold appears at 9, 10, 14, 18 and 22 karat, and rose gold at the same karats. 9 karat yellow gold is 37.5 % gold and 18 karat yellow gold is 75 % gold; both are yellow.1
| Colour | What gives the colour | Karats listed in the table |
|---|---|---|
| Yellow | Silver and copper | 9, 10, 14, 18, 22 |
| White | Palladium or silver | 9, 10, 14, 18 |
| Rose | Copper | 9, 10, 14, 18, 22 |
The additions in the table are mixtures commonly used in the industry; the same colour can also be reached with other mixtures.1
Same karat, different colour
The reverse is also true. An 18 karat piece is 75 % gold; if the remaining 25 % is silver and copper, the piece looks yellow; if it is palladium, it looks white.1 The gold content is the same, the colour is different. So it cannot be concluded from a darker or lighter yellow alone that a piece has a higher karat.
How is karat found out?
Karat is determined by measurement. Three methods are common at the jeweller: the touchstone, the acid test and XRF analysis. The stamp on the piece also gives information; but neither the stamp nor the colour takes the place of a measurement.
FAQ
Is deep yellow gold higher in karat?
This cannot be told from the colour. Yellow gold can be made from 9 karat up to 22 karat; the shade changes with the metals added to the alloy.
Is white gold low in karat?
No. White gold can also be 18 karat. It gets its colour not from the gold content but from the white metals added to the alloy; it is usually also plated with rhodium.
Where does the colour of rose gold come from?
From the copper added to the alloy.
If colour does not show karat, what do you look at?
The stamp gives information; for a definite karat, a measurement such as the touchstone, the acid test or XRF analysis is made.
Karat isn’t guessed. It’s measured.
Try the live analysis to see how a measurement looks on screen, or request a quote for your business.