164 



is almost loose, with Mica interposing between it and the 

 Ouartz. I add the lower specimen as a remarkable variety 

 among shattered Ouartz, diverging and divaricating in fas- 

 ciculated prisms almost approaching to spiculae ; the prin- 

 cipal Ouartz fracture being on one side or at right ? ngles 

 with them or nearly so, as if formed in another direction. 

 This is from Aberdeen. 



TAB. CCCXC. 



"When I was at the Logan Rock, well known in Cornwall, 

 I gathered this specimen within a few yards of it out of a 

 very large solid massy vein of Ouartz. It ran some length 

 into the Ouartz, but owing to ray want of time and tools I 

 could not ascertain how far. This specimen is of a close 

 hard texture, and finely polished, which approaches, what 

 may by some be called the Tourmaline variety; it has a 

 slight greenish hue when viewed so as to transmit the light, 

 and is more or less covered with the prismatic iridescence. 



