Determination of Diallage. 141 



taining crystals of Kyanite. Several other varieties from the same 

 locality, and from Piedmont, are composed of a coarser grained 

 greyish-white Saussurite ; they contain a greater proportion of 

 Garnet ; their Smaragdite is accompanied and intermixed with 

 Augite (paratomous Augite-spar), gradually increasing, so that the 

 laminae, in many instances, entirely pass into the latter species. 

 Sometimes it is accompanied by a dark-green granular mixture 

 of Saussurite and hemiprismatic Augite-spar. 



The gabbro from Bayreuth consists of greyish-white Saussu- 

 rite, and paratomous Augite-spar, of nearly the same variations 

 of colour, slightly inclining to green. The specific gravity of the 

 latter is 3.255. 



The varieties from the Bacher mountain, in Lower Stiria, 

 are among the most remarkable. In comparison with those de- 

 scribed above, they contain only a small quantity of Saussurite, 

 but a great deal of Garnet, and also Kyanite, in beautiful blue 

 crystals and grains. The large foliated masses of Smaragdite are 

 seldom to be met with among them ; more commonly their con- 

 stituent parts separate into granular aggregates of the two spe- 

 cies, paratomous and hemiprismatic Augite-spar, the colours of 

 the former being more lively grass-green or greenish-grey, whilst 

 those of the latter incline to brown, since they are, in general, 

 either leek- or pistachio-green. They also differ in point of 

 transparency, the hemiprismatic presenting a higher degree than 

 the paratomous Augite-spar. The most instructive specimens in 

 this respect can be gathered from the stone heaps prepared for 

 the improvement of the road between Windisch-Feistritz and 

 Gonnewitz, in Lower Stiria. 



I have not found an opportunity of examining the composi- 

 tion of the Norway varieties of Gabbro. To Dr NAUMANN of 

 Jena, I am indebted for several very distinct specimens of the 

 Diallage contained in the varieties from Vaage and Gulfield. 

 They are pure hemiprismatic Augite-spar, perfectly cleavable pa- 



