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About the Store | Jewelry & Gemstones
Hardness of Different Gold Alloys
As usual, the answer to a simple question is not always simple. There are many different combinations of metals which can be used to make gold alloys. There are many different "recipes" for both 9 carat and 18 carat gold alloys. A carat simple means 1/24th. So 9 carat gold must be at least 9 parts gold out of 24, which is equivalent to 37.5%, the other 62.5% can be any other metal, the commonest used being copper and silver, but nickel, palladium, zinc, and other metals are used. Similarly with 18 carat gold, which has to be 18/24, equivalent to 75% gold, the rest being composed of any other metal. You would be quite correct to guess that each different "recipe" has its own different characteristics including hardness. It is quite possible to make hard or soft "recipes" for 9 carat and also for 18 carat gold alloys, however, most common 18 carat gold alloys are both harder and harder wearing that their 9 carat equivalent.
| Alloy |
Hardness as Cast |
Maximum Annealed Hardness |
| 9 |
70 to 105 |
160 to 170 |
| 14 |
125 to 165 |
150 to 180 |
| 18 |
85 to 125 |
170 to 230 |
| 22 |
70 |
60 to 90 |
| 23.75 |
40 |
70 |
| Silver |
65 |
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| Platinum SC |
65 |
|
| Platinum HC |
135 |
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Silver = Typical Sterling Silver (925/1000)
SC = Soft Casting Alloy
HC = Hard Casting Alloy
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