Native Arsenic is my APEX Mineral. This usually occurs as inclusions in other minerals.
Arsenic sublimes with a little heat at atmospheric pressure, converting directly to a gaseous form without an intervening liquid state
Arsenic was often used during the "Bronze Age" to make Bronze harder. Arsenic was a known poison and used for murder throughout history. It has been called the Poison of Kings.
Arsenic is primarily used to alloy with Lead. Arsenic is recovered mainly as a side product from the purification of copper. Most operations in the US and Europe have closed for environmental reasons. Chromated Copper Arsenate (CCA) has been used to treat wood for rot resistance for decades. Due to environmental toxicity, CCA has been banned in much of the western world.
Arsenic is notoriously poisonous to multicellular life, although a few species of bacteria are able to use arsenic compounds as respiratory metabolites. Arsenic contamination of groundwater is a problem that affects millions of people across the world.