356 THE CANADIAN NATURALIST. [Vol. viii. 



5. Augite of the granular 

 diabase from Waeschgrund, 

 near Andreasberg (Harz) : 



powder light greenish-gray. Cu and Sb little ; As still 



less. Pb much; Co evi- 

 dent. Ni very evident. 



6. Similar augite from Koe- 



nigsberg, near Giessen : powder 



light greenish-gray. Cu comparatively much ; 



apparently enough to de- 

 termine quantitatively. Co 



evident. 



7. Similar augite from Kroet- 

 enmuehle, near Hof (Fichtel- 

 gebirg) : powder light greenish- 

 gray. Cu and Co evident. 



As in the hornblendes, cobalt has been found in very small 

 quantity in all the augites tested, while copper could not be 

 found in every one of them, although in the augite from the 

 diabase of Koenigsberg, near Giessen, and from the porphyritic 

 basalt of Liebhards enough was present to determine quantita- 

 tively. Both elements occur in the augites of very ancient and 

 also of very modern eruptive rocks. In the diabases and there- 

 with associated Schalsteine of Nassau copper pyrites occuri in 

 direct ratio as the decomposition of the rock has progressed, as is 

 proved by the numerous veins (some thirty) in the neighbour- 

 hood of Dillenburg, and some ten in the valleys of the Lahn and 

 Weil near Weilburg, which all contain ore only within this 

 rock and are richest where they intersect beds of red hematite. 

 But on passing into the Cypridiua slates, sandstones, etc., the 

 veins become barren. Galena and blende occur but rarely in 

 the Nassau diabases associated with eopper pyrites in calcspar 

 fissures or in veins of copper pyrites, as, for instance, in the 

 Fortunatus Mine, Guade Gottes and Gold Mine. Self-evidently 

 the former occurs in the diabase region only in small veinlets 

 (deserted mine Goldgraben near Weinbach, Merkenbach near 

 Herborn) or associated with arsenical tetrahedrite * (Mehlbach 



* Tetrahedrite with a maximum of one per cent, siver and galena 

 occurred frequently in separated Mitteln at Weyer, the former where 

 Schalstein, and the latter where diabase formed the immediate counry 

 rock. 



