Red phosphorus is hard enough to procure due to the strict regulations in place to make it hard for junkies making meth. The violet allotrope is even more difficult. In this case because to make red phosphorus is used as a first step and an additional process converts it to this form. A bonus, insofar as collectors are concerned at least, is that it's of little use to those intending to make drugs with it as the conversion back to the red allotrope is irreversible.

The violet (or purple) variety is also known as "Hittorf's phosphorus" after Johann Hittorf, a 19th century physicist studying what was then still a chemical novelty. Soon after the white - and by far the deadliest - form of phosphorus was used commercially to make the first carry-anywhere matchsticks. The dangers for both the makers and users were so appalling that it was soon phased out of production in favor of safer alternatives.
While the red and white strains of phosphorus would go on to play their roles in commerce and chemistry the violet remained but a footnote in academia!

In this sample is sealed a large crystal of this rare form of the element phosphorus. Reminiscent of some types of volcanic rock, each piece displays a complex pattern of colors ranging from purple to terracotta to black and the odd sparkle. Each one a unique and wonderful specimen!