6mm is not likely to be anything nucleated except Akoya, right? And it does not look white ... so probably not Akoya.
Which leaves non-nucleated versions, i.e. freshwater. And the color could well be a lighter purplish shade under some typically yellowish incandescent indoor lighting. I'd vote for this last option. The setting fits too - it looks like something straight out of a findings catalogue with the stones more likely CZ (as it gets slightly dull with handling) or even white sapphire (which is duller by nature).
I'm a pessimist...
