Amianthiform Arseniate of Copper

This species of copper appears first to have been described by Count Bournon. The present variety is a curious example, and seems so well described by the above author, that we shall transcribe part of his own words. “This variety is composed of fibres as delicate as those of amianthus, of the flexibility of which they frequently possess a certain degree.” In the present specimen they resemble the finest filaments of silk. It servest to show a variety in colour not mentioned by Count Bournon, viz. the purple hue, which more or less covers the surfaces or the points of the flexible threads. The other parts are of a lightish straw yellow. Its resemblance to a raceme of currents or a bunch of grapes made me think that each bundle was composed of fibres formed from its centre (as some of the smaller ones are): but on opening some of them we found ochraceous gravelly substance in the middle, from which they diverged more or less reguarly, often more dense and hard inwardly than outwardly. The more regular ones are commonly more white and satiny than the others, excepting towards the tips, and are more of the texture of rotten wood. The outsides are very tender, and easily bruised. According to the analysis of Mr. Chenevix, this species contains

Haüy mentions capillary arseniate of copper, v. 3. p. 578. and observes “that foreign mineralogists have found different regular forms of arseniate of copper, which from certain circumstances he has not yet been able to determine.” The lower magnified figure shows some of the fibres or filaments of both sorts here mentioned, some of which are collapsing at their points as if they had been wetted, forming various reticulations and indentations of a purplish hue, apparently retaining that colour from being less exposed to rubbing or any other accident. This was found in Huel Gorland mine in Cornwall, from whence most of the other arseniates of copper come.