94 Mr Haidinger's Description of Er mite. 



clusively, others in more beautiful varieties than in any other 

 country, in the rich mining districts of Cornwall. 



Though not at first recognized as distinct species by Haiiy, 

 who endeavoured to refer all their different forms to the same 

 type, four of them have been proved to be actually indepen- 

 dent species, not only by the characters given by Count Bour- 

 non himself, but also by the subsequent labours of later mi- 

 neralogists. 



They all belong to the natural order of the malachites in the 

 system of Professor Mohs, in which they are comprised in se- 

 veral genera, with the exception of one species classed in the 

 order mica. 



The new species, which it is the object of the present paper 

 to describe, contains arsenic acid, and copper, and undoubt- 

 edly likewise belongs to the order Malachite, and is in parti- 

 cular remarkable for its resemblance to the common green car- 

 bonate of copper, or the hemiprismatic habroneme-malachite 

 of Mohs. 



Though not presenting determinable crystals, the appear- 

 ance of the specimens in Mr Allan's cabinet, the only ones 

 which I remember to have ever met with, are highly crystal- 

 line. The individuals are arranged in concentric coats with 

 rough surfaces, produced by the termination of exceedingly 

 small crystals, the layers often not firmly cohering, so that they 

 may be easily separated from each other. These layers them- 

 selves are very compact ; they show an uneven, or sometimes 

 imperfect conchoidal fracture, and traces of cleavage. The 

 cleavage probably takes place parallel to the broad faces of 

 rectangular four-sided plates, into which the individual termi- 

 nates. I have in several instances observed something like 

 them by means of a compound microscope, but always very in- 

 distinctly. These plates form crest-like aggregations, similar 

 to those of mesole. A circumstance which greatly increases 

 the difficulty of observing the regular forms, is the complete 

 absence of lustre, the surface of the concentric layers being 

 quite dull, while there is only a slight degree of resinous lustre 

 in the fracture. 



The colour of erinite is a beautiful emerald green, slightly 

 inclining to grass green. The streak, likewise green, is a lit- 



