Lollingite or löllingite
is Iron arsenide with formula FeAs2 ,but it may contain nickel,cobalt and sulfur; the hardness is 5-5.5
Often mixed with very similar arsenopyrite ( FeAsS) ,therefore difficult to distinguish ,is only little bit softer.
It comes from Copper World Mine, Yucca,Mojave County,Arizona, USA.
Weight: 1.11 ct.