Assertion: opal | /r/HasProperty | found as nodule
Facets:
value: intrusions into sedimentary rock layers
type: LOCATION
value: often
type: TEMPORAL
value: within the solidified volcanic ash
type: LOCATION
Source sentences:
text: Because opal is known to form near the surface of the earth at relatively low temperatures where there has been volcanic activity, often opal can be found as nodules within the solidified volcanic ash we know as pumice.
text: They have been found as sheets or nodules, sometimes as a coating overlaying fossil bones or as intrusions into sedimentary rock layers.