ON GLAUCOPHANE. 97' 



original glaucophane being bluish or purple, while the other is rather 

 greenish. 



The very first step of transformation is the production of stripes 

 in the original, compact diallage, of which mineral alone the primitive 

 rock seems to have been composed, and may then be termed pyroxenite. 

 The cause of stripes or rather a lamellar structure may be sought in 

 the action of pressure, under which the rock has been subjected in the 

 the course of geological time. The action of pressure was so great as 

 in many cases to have caused an actual crushing of massive diallage, 

 and pulled it asunder in the direction of schistosity. (Fig. I.) This act 

 of mechanical deformation of rocks, accompanied by the molecular 

 rearrangement in mineral contained in them, has been so ably discussed 

 by J. Lehmann,* Ttall,! G. li. Williams,! ^^^ others that it is quite 

 unnecessary to enter into details on the present occasion, and. the writer 

 expresses but his agreement with the view advocated by the above- 

 named geologists. 



In the weak, unprotected part, that is peripheries, and fissures 

 of the mineral, paramorphosis readily begins to set forward in be- 

 coming glaucophane; the latter mineral seems, however, to be a 

 chemical nature of unstable equilibrium, and represents only an 

 ephemeral stage in tlie process of transformation; for, the secondary 

 glaucophane soon assumes a fibrous structure, and becomes crocidolite. 

 The writer observed a fact that might corroborate the above statement, 

 and it is a matter of no small importance. For microscopic examina- 

 tion, a number of slides had been prepared of specimens from different 

 localities, and glaucophane in these slides in the course of some weeks, 

 totally lost its original blue colour, and turned into a light green 

 substance. 



* Uebsr die Eatstehung der altkrystalliuischen Schiefergesteine, p. 190 et seq; 



t Q. J. G. S., Vol. XLI, 1885, p. 139. 



X Ameri. Jouru, of science. Vol. XXVIII, 188i, p. 267. 



