PROPYLITE. 83 



huge "propylite" cro^jpings of Ophir Ravine the industrious use of the sledge 

 revealed surfaces which were unmistakably dioritic, and so propylite dis- 

 appeared from the surface. Under ground it early became evident that the 

 east country rock was different fi-om that upon the surface; but a long time 

 elapsed before an accidentally protected mass was discovered, which was 

 fresh enough to serve as a basis for determination. It proved to be diabase. 

 Later, other localities of fresh diabase were found, but while in a new dis- 

 trict broad inferences might soon have been drawn as to the character of 

 the hanging wall, this was impossible in the face of previous determinations. 

 If a rock answering to the definition of propylite existed, it was necessary 

 to determine its precise area and occurrence; and if there were no such 

 rock it was indispensable to prove that the whole area was occupied by 

 others. The state of decomposition of the underground rocks is so 

 advanced, that in not more than three out of a hundred of the specimens, 

 all selected with the utmost care, is there a fresh augite or hornblende, and 

 perhaps half of the IS.'i miles of underground workings are accessible. 

 The task was therefore a laborious one. The lithological examination 

 became a protracted study of decomposition-products, and resulted in 

 proving that propylite did not exist below the surface any more than 

 upon it. 



Propyiitic habitus. — Thc Biost Striking macroscopical points of distinction 

 between the i-ocks in the Washoe District which have been determined as 

 propylite,^ and the better established Tertiary and ante-Tertiary rocks, are 

 a greenish color which often tinges the feldspars as well as the groundmass, 

 impellvicid feldspars, and a certain blending of the mineral ingredients 

 which helps to deprive the rock of those characteristics by which we are 

 accustomed to recognize fresh specimens as belonging to the older or to the 

 younger series. These appearances seem to me to constitute its "charac- 

 teristic habitus." 



Fallacious nature of the distinguishing characteristics. BarOn VOU Richtliofcn belicVcd 



that the macroscopical character of the rock was due to green, fibrous 

 hornblende, and the diffusion of this mineral in fibrous particles througli 

 the mass of the rock. This view was confirmed by Professor Zirkel, who 



' See page 88. 



