Massive Ore - Rottenstone Deposit
8.3% Ni, 4.67% Cu, 1870 ppm Co, 9.09g/t PGE's + Au
Net Texture Ore - Rottenstone Deposit
4% Ni, 1.12% Cu, 923 ppm Co, 10.48g/t PGE's + Au
Three styles of mineralization occur at the Rottenstone property. Style one; occurring within the host migmatite complex; consisting of metasedimentary supracrustal rocks, disseminated and stringer pyrrhotite occurs with minor pyrite and rare chalcopyrite, along with fine disseminated graphite.
The second type of mineralization recognized is formational semi-massive to massive pyrrhotite with lesser pyrite and chalcopyrite occurring within the metasedimentary assemblages. Locally, these formational sulphides can have significant strike length; up to and > 1.0km. These units have been interpreted to be sedimentary sulphidic iron formation and have been further interpreted to be an important source of sulphur to contaminate intruding ultramafic intrusions and trigger sulphide immiscibility within the magma.
The third style; the Rottenstone-style of mineralization, is the mineralization comprising the Rottenstone Deposit. Mawdsley (1946) described the Hall Showing (Rottenstone Deposit) to contain up to 50% sulphides in the form of pyrrhotite and lesser chalcopyrite. A whitish mineral (in reflected light) associated with the pyrrhotite/chalcopyrite was identified as violarite. Very rare tiny blebs of pentlandite were reported. Dr. Larry Hulbert (1988) concluded from examining mineralized samples around the abandoned Rottenstone open pit that approximately 50% of the ultramafic intrusion; which he refers to as a harzburgite-orthopyroxenite sill, consisted of sulphides. Most of the mineralization occurs in the form of dense net-textured sulphides consisting of pyrrhotite, pentlandite and chalcopyrite. Hulbert (1988) noted the net-texture mineralization was dominant in the harzburgites, and disseminated sulphides were more dominant in the pyroxenites (orthopyroxenite and clinopyroxenites) and occasionally massive sulphides were found in both lithologies.