Assertion: arsenic's allotrope | /r/HasProperty | black
Facets:
value: with being the most common
type: OTHER
Source sentences:
text: The three most common arsenic allotropes are metallic gray, yellow, and black arsenic, with gray being the most common.  
text: The three most common arsenic allotropes are gray, yellow, and black arsenic, with gray being the most common.
text: The Bayreuth researchers are proposing an analogous name for the allotrope of nitrogen they have discovered: black nitrogen.