Search Mineralpedia – A Mineral Photo Database and Identification Guide
Named after Louis Caryl Graton, former Professor of Mining Geology at Harvard University in Massachusetts, USA. Gratonite is a rare mineral that can be found in Peru, Cuba, Poland, Bulgaria, Germany, Switzerland, the Isle of Man, Spain, Namibia, and Japan. It occurs in vugs in hydrothermal copper deposits. Associated minerals include realgar, pyrite, sphalerite, pyrrhotite, aresenopyite, enargite, tetrahedrite-tennantite, jordaite, canfieldite, and hutchinsonite.
Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/gratonite.pdf