Assertion: amorphous boron | /r/HasProperty | dark brown
Facets:
value: to black amorphous powder
type: OTHER
Source sentences:
text: There are two allotropes of boron; amorphous boron is a dark brown to black amorphous powder, but metal-like crystalline solid is an extremely hard (9.3 on Mohs' scale), black to silver-gray, brittle, lustrous and has a bad conductor in room temperatures.