Arsenopyrite is an iron arsenic sulfide mineral with a dull silvery to gray finish. The purest form of arsenopyrite is 46% arsenic, 34.3% iron, and 19.7% sulfur.

When dissolved in nitric acid, it releases elemental sulfur. When arsenopyrite is heated, it produces sulfur and arsenic vapor. With 46% arsenic content, arsenopyrite, along with orpiment, is a principal ore of arsenic.

Arsenopyrite also can be associated with significant amounts of gold. Consequently, it serves as an indicator of gold bearing reefs.

Arsenopyrite is used in herbicides, wood preservatives, alloys, medicine, insecticides, and rat poison.
Environmental impact. Arsenopyrite is considered an unwanted impurity because it can be difficult to separate from other sulfide minerals in ores and Arsenic is a highly toxic pollutant.

Symptoms of acute arsenic poisoning include vomiting, diarrhea, vomiting blood, blood in the urine, stomach pain, hair loss, cramping muscles, and convulsions.

While not a valuable gemstone, finding a good quality specimen of arsenopyrite did take me quite some time.