The terrestrial abundance of arsenic is about 5 grams/ton being found widely dispersed in Nature. Some native samples of arsenic have been found which vary in purity from about 90 to 98%. The commonly associated impurities encountered in these samples are antimony, bismuth, iron, nickel and sulfur.

Normally, arsenic is found in Nature combined as sulfides, arsenides, sulfoarsenides and arsenites, and occasionally as oxide and oxychloride. The most commonly encountered minerals of arsenic are arsenopyrite (FeAsS), loellingite (FeAs2), enargite (CuS.As2S5), orpiments (As2S3) and realgar (As2S3).

The bulk of the arsenic of commerce, however, is recovered as a by-product from the smelting of copper, lead, cobalt and gold.