Beautiful! My grandmothers engagement ring from the 1920s was a large tanzanite ring set in yellow gold given to her by my grandfather. For the longest time we didn't know what stone it was because it blue and purple and hard to describe. Eventually we ran into a jeweler at a party who said it was tanzanite. Which is weird because supposedly it shouldn't have been available then but we never bothered to get it appraised or checked because it's sentimental value makes us almost not want to know.
It's a beautiful stone and I hope you enjoy it!