Pyrobloin is actually a significant substance in the One Piece world, much more in relation to Seastone. From what Pagaya, who was introduced during the Skypiea arc, revealed, Pyrobloin, or, is one of the chief elements comprising Seastone. This character will provide an unusual insight into what makes up Seastone, one of the highly featured substances within the series.
Pyrobloin is a "corneous particle". This scientific term means that Pyrobloin shares properties with keratin, a protein that forms the main structural component of hair, nails, and the outer layer of skin in many organisms. This proves that Eiichiro Oda really did a great deal of effort on the little things to build a scientific background for his creation.
Thus, the origin of Pyrobloin becomes directly related to volcanic activity. In one of the conversations conducted during the Skypiea arc, Conis' father, Pagaya, says that Pyrobloin is derived from volcanic eruptions. This gives a hint toward the idea of high pressure involved in the formation of this uniquely common substance. Besides, it could explain how Seastone is rare and precious on its own in the world of One Piece.
According to Marine officer Smoker, Seastone is produced in specific areas of the ocean. This immediately implies geographical limitations on the production of Seastone and thus, by association, Pyrobloin, which it is partially composed of. Probably, those areas would have vast underwater volcanic activity. It could be that the rarity of locations where it can be produced explains its value and strategic importance in the series.
One of the most interesting aspects of Pyrobloin would have to be its apparent effect on Devil Fruit users. Since Seastone contains Pyrobloin and can cancel Devil Fruits' powers, this property is greatly valued in the world of One Piece, particularly for law enforcement and those searching for counter-Devil Fruit abilities.
Some fans have even gone as far as to say that Pyrobloin is somehow connected to Devil Fruits on a deeper level. One such theory is that when the Devil Fruits are "dreams," then Pyrobloin would be the "nightmares." These fan speculations, though unconfirmed by the actual storyline, show the kinds of theories the One Piece community can come up with such mysterious elements as Pyrobloin.
There is a general misconception that the effects Seastone has on Devil Fruit users, and by extension, Pyrobloin, are products of salt and water. On the contrary, it is actually the unique properties of Seastone, probably due to Pyrobloin, that facilitate this weakening effect. The difference between the two in creating the distinction is very relevant to establishing how Devil Fruit powers work in the One Piece world.
Modulation of the effects of Seastone is possible, as seen in Wano Country's Udon prison. Special Seastone handcuffs were made that suppressed only Devil Fruit powers rather than fully paralyzing one. This therefore means that changes in concentration, processing of Pyrobloin within Seastone give different effects, adding another degree of complexity to this compound.
Knowing that Seastone is made from Pyrobloin raises several questions about the connections between locations within the One Piece world. Some fans have theorized a connection between Wano Country and Skypiea, simply because both places seem to share connections to Seastone, and by association, Pyrobloin. While this remains purely speculative, it shows how elements like Pyrobloin are intertwined in building One Piece's intricate world.
In the larger scope of the series, Pyrobloin makes up just one of many scientific elements that Oda has brought in to flesh out a sense of realism within his fictional world. Giving a tangible, almost scientific explanation for Seastone's properties allows Oda to root the magical elements of One Piece in a scheme that seems logical within the context of the story.