242 Proceedings of the Royal Physical Society. 



The silver veins are very thin, seldom exceeding half a 

 yard in thickness. They run in two directions, speaking 

 roughly. The first set consisting of several veins has an 

 average strike of E. 60° S., and a steep hade to KE., while the 

 two veins of the second system run approximately E. 15° S., 

 and hade to N. at an angle of 60° to 85°. 



In the network of veins thus formed are found the many 

 rare and valuable minerals for which Andreasberg has so long 

 been famous. The silver veins are filled chiefly with turbid 

 white calcspar containing grains, strings, and nests of quartz, 

 and occasionally fluor, while splendid drusy cavities with 

 crystallised calcite and zeolites are often disclosed. Galena, 

 blende, native arsenic, ruby silver (Ag3SbS3), antimony, 

 silver, arsenic silver, silverglance (AggS), speisscobalt 

 (smaltine), breithauptite (M Sb), and kupfernickel (M As), 

 are some of the more valuable metallic minerals from the 

 Andreasberg veins. 



(4.) The great Devonian limestone boss of the Iberg and 

 Winterberg at Grund is at places quite honeycombed with 

 fissures and cavities, some of which contain spathic ironstone 

 in workable quantities. The carbonate is often decomposed 

 into brown ironstone, and is accompanied by quartz, calcite, 

 barytes, malachite, and wad. Barytes is absent where the 

 ironstone is richest. The limestone is also traversed by an 

 argentiferous galena vein containing copper pyrites, spathic 

 iron, calcspar, etc. 



IV. GEOLOGICAL STEUCTUEE AND HISTOEY 



OF THE HAEZ MOUNTAINS. 



1. Older Paleozoic Period. 



The Hercynian, Devonian, and Lower Carboniferous forma- 

 tions of the Harz form a continuous series, in which there 

 are, so far as is known, no cases of unconformability to 

 indicate any very great changes in the physical conditions 

 under which they were deposited. The differences in texture 

 show them to have been deposited in water of variable depth, 

 but which never became very shallow till towards the end of 

 the Culm period. 



