First, Focus On the Cut
The cut of a diamond determines its shine and shape. A well-cut diamond reflects light beautifully and gives you a brilliant sparkle, whereas a diamond that is cut too deep or shallow does not reflect light as well and is considered low quality. Choose the highest quality of cut in your diamonds that you can afford. According the GIA, an “Excellent Cut” diamond is of the highest quality and also the most expensive. It will be smart of you to choose a “Very Good” if not “Excellent” grade diamond, which will still be a high-quality stone but relatively less expensive.
The shape is one of the most important aspects of buying diamonds. If you are buying a loose diamond for an engagement ring it will be a great idea to ask the receiver what they would prefer. But if you absolutely do not want to ask and spoil the surprise, then stick to a classic. The most common shapes are: round, princess and cushion-cut. Go for a non-traditional diamond shape like marquise, pear or heart only if you are sure that your partner is into that!