How to test white zircon

[absolutme77]

I have a pair of diamond jackets that I wear with various colored gemstones and pearls but wanted something diamond-like. Given the cost of 2ctw diamond studs (and wanting something similar I could actually afford) I purchased white zircon studs off eBay after seeing previous forums on Pricescope suggesting them as a great alternative. Is there a way to test to ensure that these are white zircon and not CZ? I louped them already but since I'm new at louping I have no idea what to look for. The stones seem to have the more petal like facets of OECs and not arrows like diamonds. I know that zircons are double refractive but have no idea how to look for this. Thanks.
Here are pictures of the studs:

 

[Bron357]

A presidium gem tester will tell you if they are are CZ or not. CZ tests as "glass". Any jeweller should have one and it only takes a a minute.