Bulletin, Issue 911

abundant Alma district alteration anticline barite belt Big raise biotite blebs brecciated Buckskin Gulch BULLETIN 911 PLATE calcite carbonate Chaffee formation chalcopyrite clay gouge Colo contain dolomite east Emmons extend feet feldspar fine-grained fissures galena grains groundmass Havighorst igneous intergrown Leadville district Leadville limestone Lincoln porphyry locally London fault London fault zone London Mountain London type London vein Loughlin main fault Manitou limestone marginal McDonald vein microcrystalline quartz mines minor faults Mosquito Range nearly North London occurs orthoclase oxidized Peerless shale member Pennsylvania Mountain phenocrysts places plagioclase porphyry sills porphyry zone postmineral pre-Cambrian pre-Cambrian rocks pyrite quartz monzonite quartz monzonite porphyry quartzite Sawatch quartzite sedimentary sericite SHAFT shale shaly shear zone Sheep Mountain silver-lead deposits Singewald solutions sphalerite stopes strata stratigraphic structure sulphide minerals surface SURVEY BULLETIN 911 syncline Thin section TUNNEL upper vein quartz veinlets vicinity Weber white quartzite WINZE York Mountain