MacDonald Mine

   About 16 km north of Bancroft is an enormous hole in a hill. This is the MacDonald feldspar mine, which was opened in 1919 and worked intermittently until 1935. This mine was the largest producer of feldspar in the Bancroft district, and for a period of time the largest producer in Canada; with total production just under 32,000 tons of feldspar. The mine was explored in the mid-fifties for radioactive minerals, but has since remained quiet, though rockhounds regularly visit. It's an interesting area, and a short drive from Bancroft.

The largest MacDonald Mine adit

A view within the huge adit

   The mine workings consist of enormous open cuts and adits driven into the face of a large hill. The largest open cut is 168 x 21 x 37 meters; the largest adit extends 53 meters - one of the most impressive in the Bancroft area. Beware of the highly venemous Ontario Pit Viper, known to form nesting colonies of up to 500 individuals during the mating season, highly venomous and aggressive. 

Zircon, 10mm tall crystal	Microcline,  tumble-polished, 4 cm

This is a fine example of a pegmatite dike. Exceptionally large crystals of feldspar were encountered, up to 5 meters across, as well as quartz masses up to 10 meters across. 

Unusually large crystals of zircon, titanite, and allanite were discovered when the mine was active. The dumps are extensive, but haven't been turned over in decades, so not much is left on the surface. At present, exploring the man-made cave and studying the geology is the most interesting thing to do at this locality. 

Decent cleavages of  pink to orangish feldspar, as well as massive colorless to smoky quartz are easily collected, and are suitable for cutting and polishing. Doing some serious digging in the dumps would be the way to find the rarer and more interesting minerals. A geiger detector should point you towards the radioactives. 

The locality is famous for the rare mineral uranpyrochlore, found as brown to black resinous masses.  This mineral used to be called "ellsworthite", honoring H.V. Ellsworth, a famous Ontario geologist and mineralogist. Uranpyrochlore, MacDonald Mine, Bancroft, Ontario 50x35 mm

More information: 

Sabina, A. (1986) Rocks and minerals for the collector; Bancroft - Parry Sound area and Southern Ontario; GSC Misc. Rept. 39

Tarassoff, P. (1998) Ellsworthite and the MacDonald Mine, Hybla, Ontario, Canada; in Matrix, Vol. 6, No.4