Knowing the 4 "Cs" is NOT enough to "price" a diamond accurately. Not all Gemological labs are the same. Most smaller gem labs are extensions of local jewellery stores, created solely for the purpose of raising the image of the store's inventory. Such labs are hardly unbiased and the certificates accredited by them are rarely accurate. If you want an honest assessment of a diamond's true quality, avoid any lab that is not one of these listed below:

Other labs do not enjoy the same reputation and popularity as those listed above, and therefore will not command as much value if you ever need to sell the diamond. In the worst scenario, other labs will not grade the diamond properly and you are not receiving the actual quality of diamond you want. In most cases, you will end up paying too much for a diamond of lesser quality with certificates from other labs.