Quick question on investments in Tanzanite?

I typically purchase diamond rings (as sort of something I can hand down to my children one day, where it has a likely hood of being worth something…)

I just started looking into tanzanite, and for my first purchase I bought a AA Tanzanite/Diamond ring. This ring is as follows:

3 gtw Tanzanite
.06 TW Diamonds (Clear)
Set in sterling silver

It was at a shop near here, on sale from 669.00 to 139.00… Now diamond I UNDERSTAND, but I am not familiar with this stone…The tanzanite is not one stone, it is many stones consisting of pear/oval brilliant/cushion cut. I realize it being small stones common sense tells me, it obviously is not going to be as much as a whole stone.

This is my first purchase in tanzanite, I am trying to really get a “feel” for purchasing it….i thought best with a “fashion type” ring. Is 139.00 something even worth keeping, or should I take it back…im having my reservations.

Thanks so much for your time.