1873.] "JJ- [Genth. 



Deducting this from the analysis, the composition of this slate is that 

 of paragonite, the analyses of a variety of which, from St. Gothard by 

 Rammelsberg, and of another from Pregatten, in Tyrol (Pregattite) by 

 Oellacher, I will give for comparison : 



St. Gothard. Pregatten. Oehsenkopf. 



45.14 contains oxygen 24.07 

 ; " 19.06- 



0.20 



19.26 



" " 1.74 [ 2.07 



" " 0.10 ) 



" " 4.44 



100.00 100.70 100.00 



The oxygen ratio of RO : Pt,0 3 : Si0 2 : H 2 is equal to 1 : 9.3 : 

 11.6 : 2.1 or very near to 1 : 9 : 12 : 2, which is that of damourite. 



Paragonite is essentially a soda damourite. 



The mineral from the Oehsenkopf analyzed by John does not belong to 

 this species, f 



I have above alluded to a peculiar rock, a slaty fibrolite with staurolite 

 and cyanite, found in the neighborhood of Media, Delaware County, 

 Pennsylvania, and also near the Culsagee Mine, in Macon County, North 

 Carolina, and stated that the whole appearance of these slates was that 

 of the paragonite slates of St. Gothard. After having already proved 

 the alteration of corundum and fibrolite into damourite, and that of the 

 Oehsenkopf corundum into paragonite, the question suggests itself — may 

 not the whole of the 'paragonite slates of St. Gothard and elsewhere be the 

 result of the alteration of corundum or fibrolite? 



19. EtJPHYLLITE. 



Euphyllite accompanied by tourmaline and zoisite is a very rare asso- 

 ciate of corundum at Unionville. It is undoubtedly like the others, 

 resulting from its alteration. As I had not a sufficient quantity of pure 

 material, no new analysis has been made, and really there was no neces- 

 sity for it, because the analyses of Smith and Brush leave no doubt about 

 its composition. 



The micaceous mineral, which is found with the corundum and albite 

 near Unionville, and which resembles muscovite, gave Dr. Koenig in two 

 partial analyses about 42 per cent, of silicic acid. 



This is undoubtedly the same as that analyzed by Sharpless* and those 

 of a similar per centage of silicic acid from Asia Minor and Nicaria, 

 analyzed by J. L. Smith. 



20. Jefferisite. 



Jefferisite, a species first distinguished by Prof. Brush, is frequently 

 he result of the alteration of chlorite, hence indirectly of corundum. At 

 t Dana's Mineralogy, 5 edit. , 4S2. * Dana's Mineralogy, 5 edit. , 489. 



