Assertion: crystalline boron | /r/CapableOf | form four major polymorphs
Facets:
Source sentences:
text: It forms four major polymorphs: α-rhombohedral and β-rhombohedral (α-R and β-R), γ and β-tetragonal (β-T); α-tetragonal phase also exists (α-T), but is very difficult to produce without significant contamination.