Assertion: chalcedony's color | /r/HasProperty | rare
Facets:
value: quite
type: DEGREE
value: as gemstones
type: MANNER
value: due to a distinct mineral composition
type: CAUSE
Source sentences:
text: The fire agate from San Luis Potosi is known only to exhibit golden fire; rainbow-like colors are extremely rare due to a distinct mineral composition.
text: Other colors are quite rare as gemstones because they do not often occur in gem-quality.