Dissolve realgar with one part of orpiment, with aqua fortis.
Leonardo Da Vinci, Translated by Jean Paul Richter The Notebooks of Leonardo Da Vinci - Complete (1888). Retrieved in 2019 from Project Gutenberg (https://www.gutenberg.org/ebooks/)
Put marcasite into aqua fortis and if it turns green, know that it has copper in it.
Leonardo Da Vinci, Translated by Jean Paul Richter The Notebooks of Leonardo Da Vinci - Complete (1888). Retrieved in 2019 from Project Gutenberg (https://www.gutenberg.org/ebooks/)