Assertion: alexandrite's color | /r/DistinctFrom | those of natural stones
Facets:
value: sufficiently
type: MANNER
value: to warrant further testing
type: PURPOSE
value: usually
type: TEMPORAL
Source sentences:
text: But they can usually be identified as spinel (by refractive index), and the colors of the synthetic gems are usually sufficiently different from those of natural stones to warrant further testing.