Assertion: opal | /r/MadeOf | the minerals cristobalite
Facets:
value: sometimes
type: TEMPORAL
Source sentences:
text: Opal is hydrated silicon dioxide - submicroscopic silica spheres bonded together with water and additional silica, sometimes containing the minerals cristobalite and tridymite.
text: Opal is hydrated silicon dioxide - submicroscopic silica spheres bonded together with water and additional silica, sometimes containing the minerals cristobalite and tridymite.