[nzporsche944s2]

Research the 4 "C"s - Cut, Clarity, Colour, Carat

If the diamonds are independently graded (i.e. not graded by the actual seller) then the standards should be the same wherever you purchase them from.

Weight / Size (Carat) isn't everything although it is usually the first number people look at when looking at a diamond. In my experience Cut and Colour have a far greater bearing on the appearance of the diamond than clarity or carat.

A smaller diamond that is expertly cut and very white will sparkle beautifully.

I've seen some big cloudy off-white/yellowish diamonds that are just butt ugly although technically they are large by weight (carat).

With earrings make sure both sides are identical to the eye in size and cut. That is one reason earrings can be disproportionately more expensive than the equivalent weight of a single diamond.