Assertion: precious opal | /r/CapableOf | occur as replacements of mineral grains
Facets:
value: often
type: TEMPORAL
value: as infillings of isolated tiny vesicles
type: OTHER
value: in these rocks
type: LOCATION
Source sentences:
text: In these rocks the precious opal often occurs as replacements of mineral grains or as infillings of isolated tiny vesicles.