Assertion: arrowhead | /r/MadeOf | stone
Facets:
value: of organic materials
type: OTHER
value: usually
type: TEMPORAL
Source sentences:
text: Arrowheads are usually made of stone, metal, shell, or glass, and they have a pointed end and some type of worked element which experts call the haft.
text: The earliest arrowheads were made of stone and of organic materials; as human civilization progressed other materials were used.