Assertion: rhyolitic obsidian | /r/MadeOf | sio(silicon dioxide
Facets:
value: mainly
type: DEGREE
Source sentences:
text: Though obsidian is usually dark in color similar to mafic rocks such as basalt, obsidian's composition is extremely felsic Obsidian consists mainly of SiO(silicon dioxide), usually 70% or more.
text: Though obsidian is usually dark in color similar to mafic rocks such as basalt, obsidian's composition is extremely felsic Obsidian consists mainly of SiO(silicon dioxide), usually 70% or more.