Chalcopyrite, Pyrrhotite, Sphalerite
This sample contains some common sulphide minerals, some of which are the valuable ore minerals chalcopyrite (copper) and sphalerite (zinc). The other mineral, pyrrhotite, can sometimes host significant precious metals, but by itself is not valuable.
Since chalcopyrite and sphalerite are common amongst this collection, this description will focus on pyrrhotite. Pyrrhotite is an iron sulphide mineral that is bronze to dark black in colour. Due to much more cost-efficient sources of iron such as iron stone, it is not mined unless it includes some of a more valuable commodity such as gold or silver. One very interesting property of pyrrhotite is that it is variably magnetic. This property is based on having iron in the overall mixture of elements in the mineral. Varieties of pyrrhotite with less iron are more magnetic. Pyrrhotite is often found as a constituent in mafic rocks of igneous composition, and in that case, it is associated with a more valuable mineral called pentlandite.
This sample comes from the North Rock Mine near Fort Frances, Ontario. The mine was discovered by prospectors in 1958 and mined via shaft in 1972. On this property lots of mafic and ultramafic rocks can be found, some of which are basaltic pillow lavas.
Store: Association for Mineral Exploration (AME)
Accession #: AME-158
Primary Mineral: Chalcopyrite, Pyrrhotite, Sphalerite
Secondary Mineral: –
Site Locality: North Rock Mine
Location: Fort Frances, Rainy River District, Ontario
Special Features: n/a