I would like to take the opportunity to explode a couple of myths according to the research I have done.
The 9ct is harder myth
Many people are of the belief that 9ct is the harder metal. I am also aware that they are often told this by various sales people. I have never agreed with this and now having done extensive research, have found this to be untrue. The technical answer is this. The hardness of 9ct according to the Vickers scale of hardness is anywhere from 70 – 170 depending if it is cast or manufactured and the alloy used. 18ct on the same scale is anywhere from 85 – 230. Some variation will occur due to the various “recipes” (the combination of metals to produce 9ct, 18ct etc) that manufacturers use.
That being said, metallurgy is a little more complex than that. There are different types of hardnesses such as shear, tensile, compressive etc. 18ct will bend easier than 9ct. Hard metals may be strong but are more likely to wear away. A metal with a little give will be inclined to be more durable against wear.
In reality these will likely under normal circumstance make only a small difference over the lifetime of the ring.
See our dedicated page on diamond simulants.