I started thinking about this today when I took my best friend's boyfriend (soon to be fiancee!!!

) ring shopping so he could get an idea of what she likes.
I know that traditionally engagement rings are diamonds, but my best friend also wants sapphires in hers. So that got me thinking, what is your favorite gemstone and why?
I'll get this started...
My favorite gemstone is alexandrite because it is such a chameleon. I love how it ranges from deep purple to pink to blue-green depending on what light it is in. The only hard thing about alexandrite is that it is so impossible to find natural alexandrite. There is plenty of stuff that is lab created around, and that is relatively inexpensive. But, the real stuff only comes from Russia and Africa and costs a small fortune.