Assertion: chalcopyrite | /r/CapableOf | treat with acid
Facets:
value: to produce an iridescent tarnish
type: PURPOSE
value: almost always
type: TEMPORAL
Source sentences:
text: "Peacock Ore" which is sold to many amateur mineral collectors often as a variety of Bornite, is in fact almost always Chalcopyrite treated with acid to produce an iridescent tarnish