338 Spodumene and its Alteration*. 



core was composed partly of both Killinite and Spodumene, some 

 further interesting observations were made. Near the outer 

 margin of the section, the fibres of Cymatolite, lying at right 

 angles to the contour of the crystal, were mostly parallel and 

 undisturbed. But in approaching the core, sometimes the bun- 

 dles of fibres were strongly curved, and sometimes completely 

 dislocated into a confused mass of scales. Near the junction- 

 line between the Cymatolite-erust and the core, the same curved 

 bundles of fibrous blades were often observed. Outwardly they 

 abutted perhaps against some one of the plates of Muscovite 

 (which always have been formed and lie parallel to the axis of the 

 Spodumene-crystal) : in such a case the plates of Muscovite were 

 seen to be partly dislocated, and their laminae shoved successively 

 past each other en echelon. Inwardly their apices were directed 

 against the yet unaltered core — like a forest of spears thrust 

 against a fortress- wall. Some of these apices are seen to have 

 been insinuated within the crevices of the Spodumene (or Killi- 

 nite), apparently leaving a minute sieve-like passage between the 

 serrated or drusy margin of the Cymatolite and the cracked 

 surface of the Spodumene. 



At first it had been concluded, from the many evidences of 

 distortion which the pseudomorphs present, that these were 

 merely the results of ordinary mechanical pressure, produced in 

 this granite-vein — as certainly in many others tilted at high 

 angles — by a settling of its contents in the direction of the dip 

 of the vein, and by considerable internal motion. Greater 

 familiarity with the latter phenomenon in other localities has 

 called attention to its other accompanying results — such as 

 slickensides, minute downward dislocation of crystals (as in 

 long prisms of Beryl and Tourmaline), or folding of mica plates, 

 by unecpial or sudden pressure, etc. — which appear to be com- 

 pletely wanting in this case. 



Now, the atomic volume of the triple molecule of Spodu- 

 mene is about 355, but it rises to 451 in Cymatolite. It has 

 therefore occurred to me that the pressure, which produced the 

 bending, twisting and flattening of crystals, and the apparent 

 squeezing or pinching of their terminations, may be possibly 

 attributed to an entirely different cause. These facts may pre- 

 sent a novel and interesting illustration, on a remarkably large 



