Assertion: amorphous boron | /r/HasProperty | black
Facets:
Source sentences:
text: Amorphous boron is a brown powder and metallic (crystalline) boron is black and hard and a weak conductor at room temperature.
text: Amorphous boron is a brown powder and metallic (crystalline) boron is black and hard and a weak conductor at room temperature.
text: Several allotropes of boron exist: amorphous boron is a brown powder and crystalline boron is black, extremely hard, and a poor conductor at room temperature.