What physical and optical characteristic can I use to determine it is genuine and are there known simulants or synthetics?
Chalcopyrite is always opaque so it should not exhibit asterism.
It is a common ore mineral that is sold by the ton, so simulants and synthetics probably do not exist.
Occasionally chalcopyrite displays iridescence, usually from a natural tarnish. However, sometimes people treat chalcopyrite with acid to produce a spectacular iridescence. The treated material is then sold as “peacock ore” or as a simulant of the mineral bornite.
You can find more information here https://geology.com/minerals/chalcopyrite.shtml
(disclosure: I am the author of that article)
Hey Rock Hunter,
I agree with everything you said. Are you the one that wrote on geology.com? Are you writing for them? Thats pretty interesting to read actually. Especially about what people do to make it have some spectacular iridescence.
I did write an article about one of the rarest gemstone in our company in 23 years: Topaz; http://www.navneetgems.com/23-years-to-show-the-worlds-rarest-gemstone/
Its going to be an interesting read if you get the time have a look, its not what you are expecting and to me it makes sense (self obsessed ofcouse)