18 GEOLOGICAL MEMOIRS. 



The original cause of their formation appears, however, to be con- 

 nected with the mutual occurrence of limestone and siliceous rock 

 (mica-schist and greenstone) . 



We ought certainly to mention that the limestone sometimes occurs 

 in the mica-schist of this district unaccompanied by the ores, and 

 also that very often rocks of the greenstone character and rich in 

 ores are present in the mica-schist without any limestone traversing 

 the schist in their neighbourhood. Calcareous beds or injections, of 

 but small extent, may however possibly have been employed under 

 particular circumstances wholly in the formation of such aggregations 

 of minerals. This supposition is strengthened by the analogous case 

 of the so-called [Erlanfels] in the same district, which appears to have 

 originated in an intimate commingling (by heat) of greenstone and 

 limestone. 



The Limestone at Miltitz, near Meissen, is fine, white, tolerably 

 pure, and granular ; it generally lies parallel in the hornblende-schist, 

 but at its borders it sends small ramifications into the latter. It also 

 contains fragments of the schist and even of granite and quartzose 

 porphyry, which latter it must have taken from elsewhere than its 

 own locally disturbed region (unless perchance they were present in 

 the earlier thick limestone beds). At the contact-surfaces of the 

 schist and limestone there are, at Miltitz, traces of, as it were, a 

 melting together, but few particular minerals. As such I know only 

 of Garnet, Tourmaline, and Iron-pyrites. The Tourmaline indeed 

 may have belonged perhaps to the enclosed granite fragments. 



Near Auerbach in Bergstrasse a fine granular limestone forms a 

 vein from 20 to 50 feet thick in the gneiss, granite, and syenite. Its 

 border consists in part almost entirely of Idocrase, Garnet, Epidote, 

 and WoUastonite. Disseminated in the limestone there are also 

 Hornblende, Grammatite, Iron-glimmer, Marcasite, and Copper- 

 pyrites. In the neighbouring gneiss there occur some separate veins 

 of Magnetic iron- ore. 



The Dolomite of Memmendorf near Freiberg belongs to the gneiss ; 

 it is traversed by veins, but shows no particular minerals on the 

 contact-surfaces, although it is exposed in many mines and quarries. 



The Crottendorf limestone is the most important in the Erzgebirg 

 gneiss district. In one of the large quarries opened in it, it exhibited 

 (1838) extraordinarily violent bendings and twistings of the beds— a 

 perfect jumble of curves, slips, anticlinals, and synclinals. The lime- 

 stone is snow-white, passing to greyish and reddish white, small and 

 fine-grained, and not unfrequently mixed with talc-like mica-flakes, 

 which, when abundant, produce a kind of lamination. It contains 

 Iron-pyrites, Tremolite, and Slate-spar. 



Lastly, I will here mention that the so-called Egeran (Idocrase), 

 together with Pericline, Garnet, and Grammatite, at Haslau, near 

 Eger, also belong to a granular limestone bed or vein in the midst of 

 the granite district. 



[T. R. J.] 



