what is the rarest precious stone
These terms are based on old traditions from the west. These days, all gemstones are considered precious since they are all rare and there is a limited supply of them. The traditional list of gemstones that are considered precious stones are: Diamond.
This is one of the rarest gemstones known to exist. Like painite, there are only a finite number of known pieces. Although this gemstone is not as rare as painite (there are at least several hundred around), it may be even more expensive, valued at around $20,000 per carat. The stone is a light grayish blue in color.