It is a well known fact that natural fancy color diamonds are considered to be very rare, usually a natural color diamonds can observe a single color hue or a combination of different colors, a single color hue diamond (pure color, no overtone) would achieve a higher price compare to a diamond that contains multiple color hues.
In the fancy colour diamond niche some coloured diamonds are consider to be much more rare then others, in this prestige category you'll be able to find Red diamonds, Pink diamonds, Blue diamonds, Orange diamonds, Purple diamonds and last but not least Green diamonds.
A natural Purple diamond contains a large amounts of hydrogen and boron. These two elements interact with the crystals in a very specific way which contributes the Purple shade formation, unfortunately currently there is not an unanimity regarding this reaction among the gemologist community. Some gemologist support the theory that the Purple diamonds journey to earth's mantle will motivate the stone's color hue.
A pure natural Purple diamond would be considered a very rare gem some would even say beyond rare there are, currently there are only two world famous Purple diamonds however there is a lack of information about those two stones. The Royal Purple Heart diamond is the largest fancy vivd Purple diamond known to exist. The stone weighs 7.34 carats and has an I1 clarity, the assumption is that the stone was originated in Russia.
The second world's well known Purple diamond is Supreme Purple Heart. Despite its name the diamond has a round brilliant shape (this specific type of cut would contribute the rareness even more) its exact color grade or clarity are unknown. The estimated diamond's weight range is between 2-5 carats unfortunately no one really know for sure. Just like the Royal Purple Heart diamond there isn't any certainty about the Supreme Purple Heart diamond origin, most believe that it was un-earthed from the Amazon Basin in the last 30 years.