Assertion: boulder opal | /r/MadeOf | concretion
Facets:
value: in a dark siliceous ironstone matrix
type: LOCATION
Source sentences:
text: Boulder opal consists of concretions and fracture fillings in a dark siliceous ironstone matrix.
text: Boulder opal consists of concretions and fracture fillings in a dark siliceous ironstone matrix.
text: Boulder opal consists of concretions and fracture fillings in a dark siliceous ironstone matrix.