Assertion: obsidian | /r/HasProperty | mineral-like
Facets:
value: as a volcanic glass
type: OTHER
Source sentences:
text: Obsidian is mineral-like, but not a true mineral because as a glass it is not crystalline; in addition, its composition is too variable to be classified as a mineral.
text: As a volcanic glass, obsidian is mineral-like, or mineraloid, but is not a true mineral.