Assertion: opal | /r/CapableOf | occur as nodule
Facets:
value: as cavity filling
type: MANNER
value: as closely-spaced layers
type: MANNER
value: as a replacement of wood
type: PURPOSE
Source sentences:
text: Opal also occurs as nodules and masses, as cement in sandstones, as vein and cavity fillings, and as a replacement of wood.
text: Opal occurs in the nodules as stratified cavity filling or closely-spaced layers, generally less than 0.1 inch thick.