Assertion: emerald | /r/HasProperty | valued by people
Facets:
value: because of their rarity
type: CAUSE
value: over the ages
type: OTHER
value: highly
type: DEGREE
value: because of their beauty
type: CAUSE
Source sentences:
text: Emerald (beryl - beryllium aluminum silicate), ruby (corundum - aluminum oxide), sapphire (corundum), opal (silica) and diamond (carbon) are all minerals and have been highly valued by people over the ages because of their rarity and their beauty.