I had mine made into a necklace. But after I remarried, my DH commented every time I started to wear it that "I guess I don't buy you enough jewelry... you're wearing that"! So last week, after 13 years, off to auction it went! Successfully! And now I will buy myself something that doesn't have ties to my first marriage. Just my experience...
How does he know it was your original engagement diamond. I don't tell my husband the details of all my jewerly. I am not divorced, but I have items that were gifts from family or that I purchased myself over the years - he has no idea what came from where and would never even ask.
It seems a bit overbearing to me that a man would be that invested in my jewerly box.