Here is a quick check list that you need to go through when you are buying white pearls:
1. What is the origin?
Make sure they are either freshwater or Akoya. Costume pearls, shell pearls, faux pearls, imitation pearls - aren't real pearls.
2. Are the pearls round?
This is the most common pitfall. Very often vendors emphasise the lustre, and you think you are getting an amazing deal... Make sure you look at the shape. More often that not you will get button or potato shape pearls. Nothing wrong with them, but they don't have that same versatile classic appeal that neatly round pearls do.
3. What is the clasp like?
If in doubt, get a lobster clasp. It is the safest and most convenient for a woman to use. If you are trying to get the best deal, avoid gold. It makes the pearls much more expensive. Taste differ, but silver will probably do just as well as another precious metal.
4. What is the grading?
Grading is very tricky and can be gamed. However, I have a rule of thumb for you. If it is below AAA, you probably will find yourself shopping for another string soon. The dear thing is the cheap thing, as the old adage goes.
5. What is the packaging like?
It is important to pay attention to this especially if you are giving a gift. A great unboxing experience, the suspense... really changes up the mood. In any case, you will have to store the pearls separately from your other jewellery. You see, pearls are resilient, but metal jewellery can leave lots of tiny scratches - causing the pearls to lose their lustre which arises from an even surface.
6. Are they knotted?
Knotted pearls are generally easier to deal with because it ensures that you won't lose any pearls, but it's a relatively minor point.
7. What is the size of the pearls?
Size is a matter of taste. It is generally not advised to give a woman over 16 year of age pearls below 6 mm - unless she has a very slight frame. Similarly, pearls above 9 mm tend to look a little imposing on younger ladies. 7-8 mm is a good size.
8. What is the length of the necklace?
16-18" is the most versatile size. Longer necklaces tend to only be suitable for occasional wear.