What does it look like?
What is it?
Very similar to ‘fool’s gold’ but with a toxic twist, this is Arsenopyrite. It’s the most common Arsenic containing ore and is very similar in look, setting and structure to pyrite, which is one of the reasons that makes it deadly. Many have picked it up on a hike, thinking it was pyrite, only to end up with Arsenic poisoning. One way to tell between Arsenopyrite and normal pyrite is to strike the mineral will a hammer (while wearing safety goggles of course). Arsenopyrite will emit a strong garlic smell when hit, that is the tell-tale sign that of arsenic.
Where did the structure come from?
This is structure #9000109 in the open crystallography database