Blue Carbonate of Copper

This splendid variety of a well known and British mineral is so extraordinary both in form and size, that I thought a figure of it would be acceptable. The primitive form of blue Copper has been determined by Bournon to be an upright rhomboidal prism of 56° and 124°: this form is strongly marked in the larger specimen before us, and is modified by truncatures of the acute solid angles and bevellments of two of the edges of the base, and two of the terminal edges, as shewn in fig. 1. Fig. 2 has crystals of a more complicated form, where all the solid angles are truncated, the same horizontal edges as before mentioned bevelled at a more acute angle, the obtuse vertical edges truncated, and each of the acute vertical edges replaced by two faces alternately inclined towards the horizontal edges. These crystals are attached to a mass of the same substance, and in some parts are cloathed with, or even apparently changed into velvetty green carbonate of Copper. Both specimens are from Chessy, where they were imbedded in impure carbonate of Magnesia and Iron Ochre; see tab. 99.