68 



Case 64, 7926, Ottery Lode : an imperfect crystal, showing the char- 



acteristic form of tinstone ; it consists of a square prism capped 

 by a square pyramid, all the edges being bevelled. 



Crystal of Tinstone, showing prism and pyramid 

 faces with bevelled edges. 



1665, 1666, and other specimens from the Yankee Lode, show 

 quartz crystals with tinstone embedded in them. It is evident 

 that the tinstone has formed first, and the silica has crystallised 

 round it at a later date as quartz. 



4453, Ottery Lode : shows a twin crystal, a very characteristic 

 mode of crystallisation for tinstone. 



Elbow-shaped twin crystal of Tinstone. 



7783, Mole Tableland, shows the termination (?.e.,the pyramid 

 portion) of a quartz crystal invested by a layer of tinstone half 

 an inch thick. This is a particularly interesting specimen. 



Among other places, crystals are exhibited from Deepwater, 

 Emmaville, Oban, Glen Tnnes, Tnverell, Stannifer and Pheasant 

 Creek. 



