Rare old crystal of Realgar from Black Diamond Test Well, Black Diamond, Washington, USA - an oil test well driven by Shell Oil Co. in 1947. It comes from the collection of Maurizio Sprovieri, Italy with a label. On a white base grows single 7mm Realgar crystal. It has dark red color. The crystal is well crystallized. The contrast is nice. In excellent condition. On acrylic base., Interesting!