After BDM is arrested via nought module, it is harvested via Quintessential Accretion, typically in crystalline form.
Most commonly, the BDM condenses in layers around the nought module. Left alone long enough, these accretions will form crystals that can then be applied into a multitude of applications.
In regards to BDM’s natural state:
Naturally occurring Quintessential Accretion follows a much different path that results in the birth of a new symbiotic-hybrid being between human and BDM. Riarin refers to these beings as Mimicrons.