Mineralpedia Details for Penfieldite
Named in honor of Professor Samuel Lewis Penfield, a mineralogist and mineral chemist at Yale University in Connecticut, USA. Penfieldite is a rare mineral found in Greece, Italy, and Chile among a couple other localities and forms as “an alteration product of lead-bearing slag immersed in seawater” and in oxidized lead deposits of hydrothermal origin. Penfieldite is soluble in water and leaves behind a yellow-white lead-oxychloride residue.
Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/penfieldite.pdf
Penfieldite from Margarita mine, Sierra Gorda dist., Antofagasta, Chile
Doubly terminated from 0.5 to 2mm, white to clear or light blue and striated associated with Boleite as micro coatings.