Assertion: iron tourmaline | /r/HasProperty | black
Facets:
value: usually
type: DEGREE
Source sentences:
text: Iron tourmaline is usually deep black; it resembles black hornblende, but can be distinguished by the grooving and absence of cleavage and the extreme hardness.
text: Iron tourmalines are black, and the magnesium type is usually yellow or brown, but it may also be black.
text: Iron tourmalines are black, and the magnesium type is usually yellow or brown, but it may also be black.