Presidium. Call Andy at Stuller, he usually has something on sale.
Dual diamond/moissanite. Best to learn what a diamond looks like
too, moissanite doubly refractive, read thru on CZs, white sapphire
refraction usually obvious(though they can take allot of heat anyway
if not quenched). dirt, size, some bezel sets and oddball stones
don’t seem to test right with a tester anyway.