Assertion: obsidian | /r/HasProperty | brittle
Facets:
Source sentences:
text: Obsidian is hard, brittle, and amorphous; it therefore fractures with sharp edges.
text: This type of break occurs because obsidian is brittle, and an amorphous material that has no natural stress lines or planes of separation.
text: Obsidian is hard and brittle and that is why it fractures with very sharp edges.