Assertion: opal's water | /r/CapableOf | seep into crack
Facets:
value: millions of years ago
type: TEMPORAL
value: in various rock formations
type: LOCATION
Source sentences:
text: The most followed belief is that opals are formed by water seeping into cracks in various rock formations, evaporating away until all that is left is silica gel-like substance which then hardens over millions of years and turns into one form of opal or another.
text: The most accepted theory for Boulder Opals is that millions of years ago water seeped into the cracks and crevices of the ironstone and sandstone rock formations of Western Queensland carrying silica material with it.