Assertion: stone's gemstone | /r/AtLocation | gem quality
Facets:
value: so infrequently
type: TEMPORAL
Source sentences:
text: Rare or unusual gemstones, generally understood to include those gemstones which occur so infrequently in gem quality that they are scarcely known except to connoisseurs, include andalusite, axinite, cassiterite, clinohumite and red beryl.