350 On the Paragenetic Relations of Minerals. 



in the " Hoff auf mich" mine at Gbritz and other places. 

 Uranite has been found at the surface upon narrow granite 

 dikes near Schneeberg ; and other minerals containing phos- 

 phoric acid — as kakoxen, beraunite, stilpnosiderite, sorda- 

 walite, and vivianite, &c. — occur in the same manner. The 

 same holds good with regard to the cupreous phosphates. 



Taking all these circumstances together, it is hardly pos- 

 sible to form any other inference than that the minerals in 

 question, or at least the phosphoric acid they contain, origi- 

 nates from the surface, and in all probability from the decom- 

 position of organic substances. 



It must not, at the same time, be forgotten that apatite — 

 the most frequent of the phosphatic minerals — occurs as an 

 original constituent of granite, syenite, nephelin rock, and 

 in tin lodes and primitive limestone. This phosphate cannot 

 be regarded as similar, in respect to its formation, to the 

 above-mentioned minerals, and it is also singular that they 

 are not found in rocks containing apatite. 



It is possible that the chlorine of horn-silver has been de- 

 rived from the surfaces, for this mineral is found only in the 

 upper parts of lodes. 



General and partial alteration of lode minerals, aud the products 

 resulting therefrom. 



The alterations in mineral veins, although on a smaller 

 scale than in the rocks, are much more frequent and remark- 

 able. It is not from the rarer pseudomorphs that these alte- 

 rations mustbe inferred; whole generations of lode substances 

 have disappeared. Lodes containing heavy spar, fluorspar, 

 and calcspar, have been entirely destroyed ; and their former 

 existence is indicated only by the pseudomorphic substances 

 bearing their form. The chemical elements of some lodes 

 have in part remained, but the sulphurets have been converted 

 into oxides, hydrated oxides, or oxy salts, &c. There are even 

 regenerated minerals. 



There is scarcely a single lode formation which does not 

 present some products of alteration. 



It cannot be doubted that water has in many instances 



