Black Phazon Crystals are clusters of crystallized Phazon found on Phaaze. They are often mined for use in Space Pirate Trooper armor, but they lose their black appearance in the process. Larger formations of it are extremely resilient, resisting anything short of a Hyper Missile blast. Smaller formations can be destroyed by a mere Hyper Beam shot.
Logbook entry
Metroid Prime 3: Corruption: "The hardened exterior of Black Phazon Crystals is resilient to normal attacks. These structures will form naturally over time in areas with high amounts of Phazon. It is commonly mined by Space Pirates for use in producing trooper armor, but loses its darkened appearance in the process."