Canadian Rockhound: Rubellite

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Rubellite
By Richard Gunter

Rubellite. Photo courtesy of theImage.com.

Tourmaline is a relatively common mineral at the TANCO pegmatite mine, Bernic Lake, Manitoba. It occurs as black "schorl" crystals in the wall zone, and as disseminated, 0.5-1 cm long elbaite crystals, mostly green with rare bi-coloured crystals, in albitic portions of the pegmatite.

This column is a description of a third type of tourmaline found in the spodumene zone on June 25, 1997 by Peter Vanstone, TANCO's chief geologist. It has been referred to as rubellite because of its medium to dark red colour, which is very similar to that of the tourmalines from the mines at Pala, California. The crystals are abundantly fractured and unfortunately not gemmy. They occur as thin striated "pencils" with a length to width ratio of about 20:1. The rubellite is embedded in albite and quartz and there are no prominent termination faces. The crystals form crude fans of centimetres long, commonly with aggregates of smaller, 2-4 cm long, crystals growing from the faces of the larger rubellites. Associated minerals are albite and quartz with minor pollucite, beryl, and "ball-peen" mica. A minor amount of a tantalum oxide mineral also occurs with some of the rubellite specimens; it is thought to be related to microlite, but has not been micro-probed yet.

The rubellite is currently being investigated by Julie Selway at the University of Manitoba, who has determined that the tourmaline is zoned with an elbaite rim and a core of a new tourmaline species named "rossmanite" (approved name but awaiting publication). Dr. Petr Cerny is investigating the tantalum oxide mineral. At least one new mineral has been found associated with the TANCO "rubellite" and there may be more!

– For more information on the TANCO mine, see The Pegmatite Minerals of Bernic Lake, Canadian Rockhound, Winter 1997.

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The preceding article was first published in the October 1997 issue of the Mineral Society of Manitoba newsletter. Reprinted in the Canadian Rockhound with permission from the author.