Arseniate of Copper

This is the third variety of Arseniate of Copper, which the Count de Bournon calls the acute octaedron, in which the more inclined planes meet at an angle of 84°, and the others at an angle of 68°. The first variety or obtuse octaedron is figured in tab. 31. and 32., and the second variety in hexaëdral plates tab. 37. The present is mostly of a darker colour than the others, and is commonly of a bottle-green as it is called, viz. a dark blackish green. Like many other crystallizations it is somewhat rounding, but mostly with concave faces, which are here noticed in the geometrical figure as well as the straighter one, and also the manner of the elongation of the octaedron towards forming a prism, which it often assumes by being placed on one end; thus at first sight giving a new idea, and forming a four-sided prism with a diëdral summit.

By the analysis of Mr. Chenevix, this variety is found to contain,