Tantalite

Tantalite is a variety of the same mineral as was named Columbite by Hatchet, which we have figured at tab. 6: Eckeberg described it from a variety in grains and ill-defined crystals, imbedded in a reddish granite, found at Brokärns Zinnsgate, in the parish of Kemito, in Finland: a similar variety has been since found at Broddbo, in the same mine with the Gadolinite, which it very much resembles in external appearance, but may be distinguished from it by its infusibility. The most interesting variety is the one represented in the present plate, from specimens of Mr. Heuland’s, as its crystals are pretty well defined, especially the large most magnificent one, an equal to which is not supposed to exist: one approaching it is in Du Dree’s collection. It is a rectangular prism with two broad striated sides; the narrow side is smooth and shining; the solid angles and shorter horizontal edges are truncated: each of the vertical edges is also replaced by two almost linear facetts. The rectangular prism is probably the primitive form. This variety is imbedded in a whitish friable Granite, the Feldspar in which is decomposing; found in the Bohmisch Waldgeberg, not far from Bodenmais in Bavaria.

The following analyses have lately been published by Berzelius, (see Annals of Phil. 9, 74 and 76).