IDRIA. 39 



of t.lie strata in wliicli the ores are found to be greatly exao-gerated, but sub- 

 sequently inversion of the strata was proved both by structural evidence 

 and by tlie discovery of satisfactory fossils. 



The principal fissure on which dislocation took place can be traced on 

 the surface. It is also exposed in the mines, where the crushing and crum- 

 pling of the Triassic beds which it traverses are plainly visible. The attend- 

 ant parallel fissures are likewise exposed by the workings. The Triassic 

 strata belong to various subdivisions of the Alpine Trias (Werfen, Gutten- 

 stein, Wengen, and Ikonca groups). Lithologically they consist of schists, 

 sandstones, and more or less doloniitic limestones ; in short, of all the chief 

 varieties of sedimentary rocks. All of these stratigraphical divisions and 

 all of the lithological varieties of rock caiTy more or less ore in the neigh- 

 borhood of the fissures, while none of the rocks carry ore outside of the 

 region of disturbance. Furthermore, the deposits lie along the fissures, hav- 

 ing the same strike and dip as these. There is thus abundant evidence that 

 the ore deposition and the fissure S3'stem are directly related. 



The form of the deposits differs greatly in various parts of the ore-bear- 

 ing region: To the southeast the fissures cut across the beds and the ore 

 forms true and unmistakable veins filled with wall-rock, cinnabar, and gangue 

 minerals. In the northern part of the mine the fissure for some distance 

 follows the planes of bedding of the Triassic rocks and the ore is inter- 

 posed between the beds somewhat as if it were a stratum. The cinnabar is 

 found, however, not only between strata and impregnating strata, but in the 

 cracks penetrating the sedimentary beds, showing that the deposition fol- 

 lowed the disturbance and that the coincidence of the fissure and the planes 

 of bedding was due only to the fact that these, when nearly vertical, were 

 surfaces of least resistance. In short, this is a bed vein, that is, a vein which 

 happens to coincide in direction with the stratification. In the same part 

 of the mine a portion of the lower Triassic limestones and dolomites have 

 been crushed, and the deposit assumes the form of an irregular reticulated 

 deposit or stockwork. Where the rock is sandy or porous, impregnations are 

 found. 



The mineralogical character of the ore is extremely simple. Cinnabar 

 is the prevailing mineral, nf course. Native (juicksilver is found in small 



