ORDER VI. PRISMATOIDAL AUGITE-SPAR. 285 



molite, and Zoisite ; and it is likely that this will be found 

 to be true even to a greater extent, when more varieties of 

 that species shall have been discovered. The light reddish- 

 black variety from Piedmont (piemontischer Braunstein of 

 WERNER, Epldote manganesifere of HAUY) is a variety of 

 Zoisite impregnated with oxide of manganese*. 



2. The chemical composition of prismatoidal Augite-spar 

 has been found as follows : 



Zoisite Pistazite 



From the Saualpe. From Dauphiny. From Norway. 



Silica 45-00 37'00 37'00. 



Alumina 2900 27'00 21-00. 



Lime 21-00 14-00 15-00. 



Oxide of Iron- 3-00 17*00 24-00. 



Oxide of Manganese -00. KL APR. l-50.DEscoT. 1-50. VAUQ. 

 Before the blowpipe the varieties of the present species in- 

 tumesce and partly exfoliate, but are difficultly fusible, and 

 only on the thinnest edges, into a transparent glass. Those 

 which contain more oxide of iron are more easily fusible 

 than the rest. VTith borax, Pistazite likewise first intu- 

 mesces, and then yields a clear globule. 



3. Prismatoidal Augite-spar agrees in regard to its natu- 

 ral repositories with some of the varieties of the preceding 

 species. Pistazite occurs along with them, frequently and 

 in fine varieties, in beds of octahedral iron-ore ; also in 

 single drusy cavities of various rocks, without, however, 

 entering into their composition as a regular ingredient. It 

 is met with, besides, in narrow veins irregularly distribu- 

 ted through the rocks, and contemporaneous with them ; 

 also in distinct veins, where it is associated with prismatic 



* Zoisite is included in the present species, on the authority 

 of HAUY, who states its forms to be identical with those of 

 Epidote. Mr BROOKE has found a difference in this respect, 

 namely, that the perfect cleavage bisects the obtuse angle of 

 1 1 6 SO' of a rhombic prism, which is probably oblique ; and 

 that there are faces of cleavage inclined to the obtuse edges 

 of that prism. This would render it necessary to consider 

 Zoisite as a particular species. H. 



