The Estella deposit is a vein-type consisting of massive galena, sphalerite, and pyrite in a zone of fracturing and shearing within Helikian Aldridge Formation (Purcell Supergroup) quartzites and argillites. The fracture zone with the sulphide mineralization is spatially related to the contact of a Mesozoic syenite stock. Quartz is not abundant within the sulphide ore but exists in crosscutting veinlets which carry little or no sulphide. The lode ranges from a single fracture of several centimetres to a zone 4 to 6 metres wide. Locally the ore zone and/or the host stratigraphy is strongly silicified. Although there were sulphides remaining when production ceased, these were for the most part contained in the narrower portions of the fracture systems and hence would not constitute economically recoverable reserves.