Assertion: tourmaline | /r/HasProperty | enhanced
Facets:
value: by heat treatment
type: CAUSE
value: typically
type: DEGREE
Source sentences:
text: Amethyst, citrine, ametrine, aquamarine, tourmaline, topaz, light green tourmaline, sapphire, ruby, tanzanite, and blue zircon are gemstones that are typically color-enhanced by heat treatment.