Assertion: obsidian | /r/HasProperty | extrusive igneous rock
Facets:
value: usually
type: DEGREE
Source sentences:
text: Obsidian is an extrusive igneous rock.
text: We have seen in the earlier section that obsidian is an extrusive rock type and formation used to takes place on the surface of the earth when magma or lava coming out due to volcanic phenomena and rapid cooling takes place.
text: Obsidian is usually an extrusive rock - one that solidifies above Earth's surface.
text: Obsidian is an extrusive igneous rock, a volcanic glass formed by rapid cooling.