Not sure if that's the best way to look at it. You bought your wife the ring as a token of your everlasting devotion to her - there's a certain poetic quality to that token being made of the hardest substance on Earth.

You didn't buy the ring as an investment, I mean what are you going to do, take the ring back and sell it when the market is more favourable? Any profit you make will be quickly swallowed up by the divorce.