Secondary iron oxides have formed at the apex of many veins in response to circulating supergene fluids. However, the formation of secondary iron oxides is by no means ubiquitous and appears to be controlled by the postore faulting in many of the veins. Local kaolinization is present in host rocks containing phenocrysts of plagioclase. The Pickhandle is comprised of flows of dacite to rhyodacite composition, associated tuffs, and volcanic breccias. Mineralization has been deposited as open space filling along dilatant zones and as a breccia-filling.
Barite crystals are euhedral, and often one centimeter or more in length.
In many veins the barite has been brecciated and the interstices filled by later iron oxides and sulfides. Rosso calculated depth of barite emplacement at 1000 to 1500 meters. Limited analysis of quartz has yielded homogenization temperatures similar to those for barite. Barstow Formation Ian Fletcher studied the barite-silver mineralization of the Middle Miocene Barstow Formation in the vicinity of Wall Street Canyon. The Barstow which conformably overlies the Pickhandle, is comprised of lucustrine sandstones, siltstones and mudstones with minor interbedded volcaniclastics.