202 MINERALOGY AND LITHOLOGY, 



same rock is also found at Hanover, and it is a characteristic rock among 

 the valley formations, varying in color from a light to a dirty dark green. 

 At Lancaster a bright green variety is found, which contains many very 

 large crystals of orthoclase porphyritically developed, and which are 

 usually twins. It contains crystals of pyrites, which harm the utility of 

 an otherwise beautiful stone. This rock at Lancaster becomes gneis- 

 soid in structure at some points, and it is everywhere plainly a member 

 of the formation in which it occurs. At Lebanon a beautiful, green- 

 spotted variety of this rock is quarried ; but in the centre of each green 

 spot scales of biotite are seen, which indicate that the biotite has fur- 

 nished the decomposition product. In thin sections of this granite from 

 Walling's quarry the green decomposition product is seen to be epidote, 

 which in minute rounded grains is scattered most plentifully through 

 the rocks in the neighborhood of the biotite. A chloritic granite also 

 comes from Groveton. 



Granitell. Granitell is the rock in which all the chief accessories of 

 granite are characteristically absent. It therefore lacks the spotted char- 

 acter of ordinary granite. It is a rock of limited distribution, and in 

 New Hampshire cannot be called typical of any great formation, as are 

 some of the other varieties of granite. 



On Little Ascutney mountain there are granitell rocks, which, on ac- 

 count of decomposition, are yellow in color, and which contain little else 

 besides quartz and orthoclase. For microscopic study they furnish beau- 

 tiful specimens, since the quartz is filled with cavities of unusual size; 

 and in the cavities cubes of salt, also, of unusual size are found. It is 

 interesting to note that some cavities contain a cube that fills half the 

 whole space. The cube is packed into one end, while the bubble occu- 

 pies so much of the other end that it appears as though the volume of 

 the water were quite small. The apparent great variability of the rela- 

 tive amounts of fluid, salt, and space, would, however, make any general- 

 izations impossible beyond such as were made by Sorby, that the quartz 

 must have crystallized at a temperature below the critical point of water, 

 in order to allow of such powerful solvent action as is indicated by the 

 large amount of salt in solution. 



At Bemis brook, in the White Mountain Notch, there is a granite with 

 so little mica that it is almost granitell. Another, of but very local 



