I recently purchased a moissanite[1] ring and was very happy that it was a choice. My disillusionment with diamonds started when I read this article[2] on how the industry manufactured demand. The argument against diamonds and for moissanite is succinctly made by http://diamondssuck.com/ (I have no affiliation. I am just grateful that the author made it, and I try to share it as much as possible.)
I have a moissanite wedding ring; it's very popular among my mid-30s social circle. I prefer it over diamonds, both for ethical reasons and material science nerd reasons.
They're pretty, but they're not diamonds. They refract the light differently. They're more colorful. I can spot one from several feet away. We went with a man made diamond and love it. Less than half the price of an equivalent natural stone.
[1]: https://en.wikipedia.org/wiki/Moissanite
[2]: https://www.theatlantic.com/international/archive/2015/02/ho...