Can the wife tell the difference between a diamond and a CZ unless you tell her?
Yes. CZ's get cloudy and will abrade over time. The edges round off. A diamond? No. Try a Moissanite. Harder than a sapphire (Moissanite is 9.4 on the Mohs scale, while the sapphire is only 9). The Moissanite has almost two and half times more fire than a diamond.
sure. Diamonds have carbon flaws. CZs don’t. And I’ve had more than a few CZs turn grey. I can fake out my friends with a one carat but a 3 carat CZ, no way -no flaws under a loop and I’m not in the social class of flawless diamonds. And the larger they are, the more they don’t have the platinum flash that diamonds do - they’re more ‘clear-ish’ if that makes sense.