Mineralization occurs primarily as very fine grains of sulphides (sphalerite, galena, argentite), oxides of zinc (hydrozincite, smithsonite) and lead (cerussite, plumbojarosite
Plumbojarosite has also been identified in some of this material (R.
Within the oxidized zones, the primary sulfide minerals were commonly converted to limonite, pyrolusite, cerussite, anglesite, argentojarosite and plumbojarosite
(basic sulfates of Fe), and native silver, with traces of malachite and azurite.
The gossan is composed primarily of goethite, quartz (Si[O.sub.2]), beudantite (Pb[Fe.sub.3](As[O.sub.4]) (S[O.sub.4])[(OH).sub.6]), jarosite ((K,Na)[Fe.sub.3][(S[O.sub.4]).sub.2][(OH).sub.6]), plumbojarosite
[(Pb[Fe.sub.6](S[O.sub.4]).sub.4][(OH).sub.12]), argentojarosite (Ag[Fe.sub.3][(S[O.sub.4]).sub.2][(OH).sub.6]), bindheimite ([Pb.sub.2][Sb.sub.2][O.sub.6] (O,OH)) and scorodite with accessory cinnabar (HgS), native Ag, Au, and cassiterite (Sn[O.sub.2]) (Boyle 1995).
The lead and precious metal values are suspected to come primarily from plumbojarosite
Vein Minerals Adamite Goethite Arsenopyrite Gold Austinite Hemimorphite Barite Malachite Beudantite Mimetite Calcite Smithsonite Cerussite Sphalerite Chalcopyrite Plumbojarosite
Chlorargyrite Pyrite Chrysocolla Rosasite Conichalcite Tetrahedrite Fluorite Willemite Galena Wulfenite ACKNOWLEDGMENTS
The next section of the manto was named the Gypsum Pillar section; it extended for 125 meters, and yielded the first substantial production of hard, high grade lead ore enclosing lenses of plumbojarosite
(containing 16% lead) in a bed up to 10 feet thick overlying a gypsum layer.
The pyromorphite occurs as richly brown, medium-lustered hexagonal prisms, some hoppered, to 3 cm long and 1.5 cm across the tops, in jumbled groups, either loose or on yellow-brown microcrystallized plumbojarosite
The mineralogy and geochemistry of this gossan have been described by Nickel (1982), who noted the occurrence of a number of secondary ore minerals including malachite, azurite, chrysocolla, pseudomalachite, cerussite, alunite, jarosite, plumbojarosite
, osarizawaite, plumbogummite, duftite, mimetite, fornacite, wulfenite, mottramite, iodargyrite, native silver and a silver-mercury amalgam.