There is also a People's Jewelery downtown, it is also a big jewelery store. At least that's what I remember, if not still there, then you can always go to Chinook Mall, one of the biggest mall's in Calgary South. Good luck with your travels in Calgary.
Good suggestions so far...J Vair & Brinkhaus (downtown) for total $$$$$$ bling. Calgary Jewellers on 17th too. Jewels by Maxime is in the Chinook and Market Mall--high end brand name stuff tho. I buy lots at Fleetwood Jewellers but they are out in a Professional Center on Heritage, not close to where you might be DT.