Arsenopyrite

Star shaped Arsenopyrite twins as inclusion in Quartz from Dodo.

Arsenopyrite from Dalnegorsk

While polishing a dunite rock sample from Nizhne Tagil, I discovered these blocky crystals. 
I thought they might be platinum.... Thanks to the analytical effort of prof Jacques Jedwab I
now know these are arsenopyrite crystals with microscopic galena inclusions.
[photo's/collection: Maurice de Graaf]