2^$ PRIMITIVE GYPSUM. 



Analysis by ]\f f. Allan sent a specinien of this nnineral to Mr. Ekc- 



Mr. Ekeberg. , , i i • . i r i mt 



berg, who analysed it in the course of last summer. The 



constituents which he obtained, as he states them in a letter 



to Mr. Allan, are as follows : 



Silica, • 3f>* 



Alumina, • 32* 



Soda, 25. 



Muriatic acid, 6*75 



Oxide of iron, • 0*25 



10000 



V Thi« . .suit does not difFtir much from mine. The quan- 

 tity of muriatic acid is much gre'citer than mine. The lime 

 and the volatile matter, which I obtained, escaped his no- 

 tice altoo^ether. If we were to add them to the alumina; it 

 would make the two analyses almost the fame. No mine- 

 ral has hitherto been found containing nearly so much 

 soda as this. Hence the reason of the name by which I 

 have distinguished it. 



VIII. 



Account of a Primitive Gypsum, By Mr, Dausuisson, 

 Mine Engineer*, 



»,n'[f; Ji"«,?r, ^"* An a visit I have iust made to the mine of Cogne, I had 

 inuiTe gyp- ** . 



sum. an opportunity of observing a mineralogical fact, that may 



be thought not uninteresting, the existence of a stratum of 



primitive gypsum, intercalated in the mass of the Upper 



OrJy one pre- xXXi^, Mineralosrists have hitherto noticed onW a single in- 

 vious instance,. ^ . ,° ,. juatt^iu 



stance of such gypsum, discovered by mr. t^nesleben at 



the southern foot of St. Gothard in a micaceous schist ; and 

 and this 8ome doubts have been started respecting the period as- 



signed to the formation of this rock. I trust the particulars 

 I shall relate respecting the situation of that at Cogne will 

 evince the existence of really primitive gypsums; accord- 



* Journal des Mines, vol. XXII, p. I6l. 



ingly 



