Assertion: tourmaline's variety | /r/CapableOf | differ in color
Facets:
Source sentences:
text: Some varieties of onyx differ in color, such as sard onyx, which has a brown base and white upper layer, cornelian onyx, which has a red base and white upper layer, and niccolo onyx, which has a very thin upper layer, allowing the black base color to show through as grey or blue.