Canadian Rockhound: Beryl

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Beryl
By Richard Gunter, Winnipeg, MB, Canada

This article focuses on specific localities of beryl in Manitoba. Beryl is a beryllium aluminum silicate, as indicated by its chemical formula, Be₃Al₂Si₆O₁₈.

Tanco Mine, Bernic Lake
The most well known beryls from Tanco are the flattened, hexagonal, white crystals embedded in quartz from within the main pegmatite. These crystals are generally 1-5 cm in width. They contain high levels of cesium which causes the unusual shape and colour. A spectacular cabinet size specimen of crystals up to 10 cm across is on display at the Provincial Museum of Alberta; this was originally acquired from a Tanco miner by our own Greg Hasler. A minor occurrence of secondary beryl occurs in the late alteration sequence of Tanco. It is pink and has a high cesium content as well but is not very common.
Gemmy, 1-2 mm, golden yellow, prismatic beryl crystals occur in small vugs in the albite zone of the Tanco Mine. The albite is found in the fill used by the mine for the road causeway across the Bird River. This fill was excavated from the west end of the pegmatite. The vugs are relatively numerous in hand size pieces of porous, reddish albite. Most cavities contain only albite or quartz but occasionally beryl, elbaite, fluorite, switzerite and tantalum oxide crystals are found. None of the crystals are larger than micromount size but all have sharp faces and some are quite complex

Cross Lake
The Cross Lake pegmatite group is chemically zoned. Pegmatites contain either a columbite-beryl suite or a beryl-phosphate suite. The beryls from the columbite-beryl suite are subhedral (moderately well formed crystals), opaque white, and have a pronounced basal parting. They are associated with quartz, albite, columbite and spessartine, and are 2-4 cm in diameter.
Beryls from the beryl-phosphate suite are sauterne-yellow in colour and translucent to transparent. They range in size from less than 1 cm to more than 10 cm long. The larger crystals are commonly "shells" of beryl surrounding aggregates of quartz, tourmaline and muscovite. the "shell" is probably a result of fast growth conditions. The beryl is associated with quartz, albite, tourmaline and abundant blue-green apatite. It is not directly associated with the bobfergusonite suite of phosphates.

Copyright ©1997 Richard Gunter
E-mail: pamrichg@mb.sympatico.ca
This article may not be copied, distributed or reprinted in any form without the author's permission. To contact the author, please use the e-mail address provided. If you are unable to contact the author, please contact the Canadian Rockhound. Authorized reprints must acknowledge the author, original source and the Canadian Rockhound, and include the website URL address of the Canadian Rockhound.
The preceding article was first published in two parts in the April and May 1996 issues of the Mineral Society of Manitoba Newsletter. Reprinted in the Canadian Rockhound with permission.

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Document Number: win97_beryl