The Paragenetic Relations of Minerals. 99 



The same remark applies to the beds of brown iron ore 

 in the zechstone of Thuringia, which consist chiefly of altered 

 spathic iron — accompanied, when this was manganiferous, by 

 the usual varieties of wad, — tile ore, and copper pecherz, mala- 

 chite and copper lazure, resulting from the alteration of 

 copper pyrites, and even unaltered copper pyrites and fahlerz. 

 The only difference is, that the metamorphism in this in- 

 stance would have been aqueous. If this is really the case, 

 these Thuringian deposits would correspond with the very 

 frequent lode formation bearing spathic iron, heavy spar, 

 copper pyrites, &c. 



The so-called primitive limestone and dolomite occurring as 

 true beds in the older rocks, are objects of particular interest 

 to the geologist, and their origin has not yet been satisfac- 

 torily explained. They differ from the ordinary limestones 

 and dolomites, in containing imbedded in their mass silicates 

 and aluminates, as for instance the Teufelstein (Saxony), in 

 which even garnets and epidotes occur. But the same kind 

 of white crystalline limestone, sometimes passing into gra- 

 nular calcite, occurs in enormous masses, generally without 

 any very definite outlines, and in their general characteristics 

 somewhat resembling lodes, as well as in smaller masses 

 which differ still less from true lodes. They moreover pre- 

 sent a remarkable abundance of imbedded minerals. Various 

 opinions have been entertained as to their real nature and 

 origin. Their analogy to lodes is in many instances indis- 

 putable, as for example at Wunschendorf, Lengefeld, Boden, 

 Miltitz, Tharand, &c. (Saxony), at the Bergstrasse on the 

 right bank of the Rhine, and the Cipollino-stock at the 

 Kaiserstuhl (Baden), in the centre of a volcanic cone. This 

 perhaps applies equally to the similar masses of limestone in 

 Scandinavia, Finnland, the Banat, Servia, the Alps and the 

 Pyrenees, as well as to the red limestone of the island Tyrie. 

 It is indeed probable that the masses ejected from Vesuvius 

 are derived from such a mass of limestone. Finally, the crys- 

 talline limestones of North America, so rich in beautiful 

 minerals, must be included in the same class. 



In these lode-like masses there are no layers parallel to the 

 saalbands, but the entire mass is granular, almost always pure 



g2 



