The No. One occurrence occurs in the "No. 1 Limestone" which is intercalated between dark-grey argillites of the Mississippian- Pennsylvanian Milford Group. Small intrusions of "gneissic granite" are reported in the vicinity of the deposit.

The deposit consists of replaced limestones along a shear zone (northwest 45) and brecciated host rocks near or at the upper contact of the "No. 1 Limestone" with black argillites. The ore is generally oxidized, consisting mainly of iron oxide, some lead carbonates and wide silver and forming a dark brown, decomposed mass. Original sulphides are observed in places. Gangue consists mainly of calcite with locally some siderite and quartz growing in cavities in the calcite cement. Limestones in the ore are reported to be silicified.