Be very carefull … very very carefull
A diamond that is certified as G by one appraiser may not be certified as G by an independent Lab. And there are some so called independent labs that have very poor standards. So ask the person you are buying form to send it a lab that you choose and pay the little bit of the lab cost.
One more thing you have to worry about is the cut. You may have a very good diamond but if the cut is bad then it is not worth buying. The cut determines how much light is going to be trapped inside and that’s what makes the diamond shine. Jewelerrs have lights mounted on their wall in such as way that a even a poor cut diamond looks very bright. Ask you jeweler to turn the light off. You can also take a black box or paper bag with you, put hte diamond inside for few seconds, close your eye, for a few seconds so that they are adjusted to the darkness and then peek inside the bag.
Also there are plenty of fake diamonds in the market, mainly coming form russia, you will not be able to detect it, if you are not experienced. Now a days, they intentionally leave few flaws in the rock so that you will think that it is a real diamond.
Last but not least, you are buying a diamond and not the ring. In other words do not be concerned with the ring quality or size because diamond is what eveyone is going to see, diamond should always be the focal point and not the the mounting, i.e the ring. The only thing you may want to make sure is that the mounting head is made out of platinum and has enough prongs to securely mount it. So if you have a solitaire 1/2 ct rock then 4 prongs are fine, or if you have Marquie rock, you should have 6 or more prongs. The ring itself should be 14 or 18 carat gold. 22 or 24 ct gold is too soft to hold the head securely. If your lady is not planning to wear this ring all the time then you may not have to worry about all this stuff. Some basic mounting would work fine in that case. I wil not suggest white gold or platinum for ring. Because your rock is white/colorless, the rock will blend into the ring and it wil not stand out. Yellow gold will give a good contrast and so the focus is always going to be on the rock and not the ring. To me ring is just a mounting.
This is site that I hang out at and you will get some good advice and information. Just like every other website there are some sleeze bags out there to take advantage. Here’s the link http://www.pricescope.com/idealbb
My advice for everyone is to buy a diamond which has some flaws that are not visible to naked eye. Becasue fo the flaws you’ll pay less. The money you save, invest it in buying a better color i.e as colorless as you can afford.
One other thing, do not go for the size, if you buy a diamond which is too big and expensive most likely your lady is going to lock it in safe box and she is not going to wear it all the time. That’s defeats the purpose the ring was intended for. But maybe in your case it may not apply, maybe she only intends to wear ot on special occasions.
Feel free to send me a message of you need further info or clarification.
good luck