On the Paragenetic Relations of Minerals. 141 



navia. Its constituent minerals are specifically different from 

 the same minerals occurring in rocks. Pyroxene appears to 

 be the oldest member, idocras and garnet more recent. Pseu- 

 domorphs are by no means wanting. It is further remark- 

 able, that at different parts one or other mineral predomi- 

 nates considerably. Thus the accumulations of galena, iron, 

 copper pyrites, tin ore, and even limestone, have been found 

 sufficient to admit of being worked. 



The general features of this formation present great ana- 

 logy with those of the " kalkstbcken," previously spoken of. 

 While in these latter, limestone predominates, and in some 

 localities there is a much greater diversity of imbedded mi- 

 nerals, and the lode form appears less marked, the occur- 

 rence of limestone in the former is only exceptional ; but, 

 on the other hand, there is an abundance of pyroxene, garnet, 

 and pyritic minerals, which is foreign to the " kalkstbcken," 

 and the lode character is more distinctly marked. 



II. Titanium formation. — This is probably little inferior 

 in antiquity to the last, not only because it occurs in the 

 oldest known rocks, but because the essential constituent mi- 

 nerals, containing titanic acid, do not occur in any other forma- 

 tion, with the sole exception of the " kalkstbcken " and diver- 

 gent zones. Felsite is likewise found upon them, which cer- 

 tainly indicates a very remote date. 



The phenomena presented by the lodes of this formation 

 appear to admit of the following inferences : 1. That the 

 felsites are in all instances older than the compounds of ti- 

 tanic acid, or of titanic and silicic acid together. 2. Quartz 

 is generally more recent than the above minerals, except 

 rutil, with which it appears contemporaneous, and sometimes 

 even older than it. 



III. Noble quartz formation. — This occurs in Saxony, espe- 

 cially in mica-slate, sometimes in gneiss, both rocks being 

 much altered. It is older than the porphyry veins with which 

 it comes in contact, but these veins appear to bear some re- 

 lation to the richness of the lodes. The principal lode sub- 

 stance is quartz, frequently converted into hornstone, gene- 

 rally adhering firmly to the adjoining rock, and ramifying 

 into it. Large masses of ore never occur in these lodes, 



