Assertion: obsidian | /r/HasProperty | rare
Facets:
value: during the preclassic period
type: TEMPORAL
value: in the lowland areas
type: LOCATION
value: for the location
type: CAUSE
Source sentences:
text: It is rare to find obsidian older than about 20 million years, which is very youthful in comparison to most continental rocks that form the Earth's crust.
text: For example, during the Preclassic period, obsidian was a rare item in the lowland areas, found predominantly in high-status and ritual contexts.
text: Obsidian is a type of volcanic glass that was a rare commodity for the location then.
text: Older obsidians are rare since they are altered or destroyed by heat or weathering.
text: It older than a few million years is rare because the glassy rock is rapidly destroyed or altered by weathering, heat, or other processes.
text: It is rare to find obsidian older than about 20 million years, which is very youthful in comparison to most continental rocks that form the Earth's crust.
text: For example, during the Preclassic period, obsidian was a rare item in the lowland areas, found predominantly in high-status and ritual contexts.