When buying sapphires, it's important to look for natural stones that have a good color, clarity, and cut. The color of a sapphire should be rich and vibrant, and should not have any brown or gray hues. The clarity should be good, with minimal inclusions or blemishes. The cut should be precise and symmetrical to maximize the stone's brilliance. Additionally, it is recommended to look for certifications from reputable organizations such as GIA or AGL to ensure authenticity and value of the gemstone. It's also important to consider the origin of the sapphire, as some regions are known to produce higher quality stones. And finally, one should also look for the four C's, carat weight, cut, color and clarity.