Quartz occurs as drusy crystals filling voids in brachipod shells, also as chalcedonic masses, locally botryoidal with vugs containing small fluorite and dolomite xls. Geodes of quartz in epidote-rich rock is reported at the quarter post between Sec. The quartz is massive and as crystals. Quartz is a component of the lithium-rich complex pegmatites in Sec. Quartz is the major constituent of the quartzite of McCaslin Mountain where it also occurs as large crystals and clusters locally in veins.
Major outcrops are in Sec.
These include at Mt. Tom in Sec. T16N R12E and near Brooklyn in Sec. This rock is well-exposed in the quarries in NW SW NE Sec. Silicification of Prairie du Chien group rocks is widespread in the Upper Mississippi Valley zinc-lead district where it is prevalent along faults and fractures. This forms massive jasperoid as well as drusy crystals.