Geology of the Harz Mountains. 237 



is a foliated rock with crystalline grains of quartz and felspar 

 resembling felsite when the foliation is subordinate, and 

 passing into sericite when the porphyroidal crystals are 

 subordinate and the foliation predominant. The felspar is 

 either orthoclase or albite. There are also semicrystalline 

 sericitic greywackes, sericite schists, green ferruginous silici- 

 fied shales, clayslates, and veins and geodes of amorphous 

 quartz, with disseminated barytes, ironglance, and albite 

 showing the characteristic triclinic striation. In addition 

 to these minerals beds of shale containing crystals of 

 karpholite occur in the S.E. metamorphic zone. The sericite 

 is a compact mass of minute muscovite scales with usually 

 a faint green colour, and bearing a strong resemblance to 

 talc, from which, however, it can easily be distinguished by 

 aid of the blowpipe. 



7. Metalliferous Deposits of the Harz.^ 



a. Contemporaneous. 



Devonian. — (1.) The famous copper and lead deposit of the 

 Eammelsberg, near Goslar, has now been proved to be a set 

 of great lenticular beds of ore in the Upper Devonian Goslar 

 shale group, which is here inverted, and thus seems to 

 underlie the Spirifer Sandstone which forms the top of the 

 hill. The beds in which the deposit lies are inclined at a 

 high angle, and it is not surprising that its true nature was 

 for long an object of keen discussion. The fact that it is not 

 a vein is proved in two ways. 



1. The deposit is not symmetrically formed with regard to 

 its hanging and foot walls as veins usually are, but consists 

 of the following series : — 



c. Fine-grained mixture of galena, zincblende, iron pyrites, and barytes 



next hanging wall. 

 b. Laminse of pyrites and galena, "melirte Erze," 

 a. Copper and iron pyrites, with some arsenical pyrites resting on pyritous 



shale of foot wall. 



2. There is perfect conformability between the rock and 



1 General descriptions of the various ore deposits of the Harz are given 

 incidentally by von Groddeck in his admirable work, "Die Lehre von den 

 Lagerstatten derErze," Leipzig, 1879. 



