Geology of the Rarz Mountains. 239 



workings coated over with stalactic crusts of these beautiful 

 minerals, and was nearly stifled with the heat produced by the 

 decomposition going on. 



(2.) Eed ironstone of Elbingerode. Between the diabase 

 tuff and clayslates of the Middle Devonian rocks in the 

 Elbingerode basin, there is a lenticular deposit of nearly 100 

 feet thick, and disclosed to a length of 4 kilos, consisting of 

 siliceous and calcareous hsematite (FCgOg), spathic ironstone 

 (FeCOg), and some magnetic iron ore (FCgO^). Another deposit 

 of calcareous ironstone occurs entirely embedded in the tuff. 

 It is mined chiefly at Lerbach, between Clausthal and 

 Osterode. Eed ironstone also occurs on the Upper Harz, 

 along with the diabase and tuff on the same horizon. It is 

 very siliceous at places, and occurs along with small 

 quantities of spathic ironstone. 



Permian. — (3.) The celebrated Kupferschiefer of Mansfeld 

 has already been alluded to. It is simply a bituminous 

 shale bed, with an average thickness of 18 inches, contain- 

 ing little particles of the following ores : — copper pjrrites, 

 erubescite, iron pyrites, galena, silverglance, zincblende, 

 kupfernickel, and smaltine. The middle of the seam is 

 by far the richest part, and has a peculiar appearance, which 

 makes it easily recognisable by those who work it. The 

 shale contains a fish fauna represented almost exclu- 

 sively by the single species Palceoniscus Freiesleheni. 

 Platysomus occurs rarely in this district. The seam is 

 much faulted at places, and in the irregular fissures thus 

 formed veins of various silver, copper, cobalt, and nickel 

 ores are found, occasionally in workable quantity. These 

 deposits are evidently derived from the solution of minerals 

 in the seam. 



The following analyses show the composition of the shale 

 at different parts of the basin.^ 



^ An elaborate account of the mines, statistics, and geology of the Mansfeld 

 district was published in 1881, entitled, "Der Mansfeld Kupferschiefer 

 Bergbau," from which these analyses are taken. 



