Arseniate of Copper

This beautiful specimen of Arseniate of Copper was lent me by my good friend Philip Rashleigh, Esq. of Menabilly. It comes from near Gwenap. The crystals are spoken of by Count de Bournon as his third variety, “perfectly regular for a part of their length, and fibrous at their extremity.” The present specimen has these crystals with apparently four sides of the octaëdron, lengthened into filaments, and divaricating a little from a centre, forming altogether a sort of brush, narrow at the base, widening towards the apex, and terminating a little abruptly in a sharp or angular point. They are of a dark dull green, somewhat transparent, the ends being generally more opaque and lighter, owing to their fibrous nature: some crystals are of a darker green colour and more confused: see the left hand figure.

The gangue is chiefly quartz, somewhat plated and ochrey, and has intermixed with it bright green arseniate? of copper in irregular granulæ: see the right hand figure.