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White gold cost more but is much more durable.

Are you sure it's LTP?
If the ring is gold but has platinum prongs they will write 14K and PLT, if it is indeed LTP it can be just a brand name.

If you have a UV light hold it over, the diamonds if they have fluorescence will reflect blue, the CZ's will not.
Blow on it with an open mouth, the CZ will hold the condensation longer than the...

With gold prices so high it can have some value as scrap.
If you know the weight, you can call 866-239-4315 and they will buy it from you even if it is 9 karat gold.