APLIl'ES ANt) PEGMATITES 



875 



may, however, become much more abundant, and instances have been 

 met, as in a large vein near Sachems head, which consists of quartz with 

 but a few feldspar crj^stals distributed throuoh it. An extreme develop- 

 ment of pure quartz is also known, and to this latter variety must be 

 referred the huge quartz vein that forms Lantern hill, north of Mystic. 

 Lantern hill is the highest elevation in this part of Connecticut and is a 

 landmark for sailors. The vein is several hundred feet across and is 

 certainly a deposit from solution, as its quartz crystals are in banded 

 arrangement; they interlock and exhibit the characteristic features or 

 '' crustification " of a typical mineral vein. At the north end the vein 

 is hard, massive quartz, but at the south end it is so pulverulent that it 

 can be dug with a pick and shovel and can even be crumbled with the 

 fingers. Its pulverulent character has been referred by the writer to 

 crushing.* It is illustrated by plate 41, figure 2. As earlier stated. Pro- 

 fessor Dana observed that the quartz veins near Stony creek were later 

 than the pegmatites, and it may well be that they mark the closing and 

 fumarolic stages of the intrusive phenomena. 



Chemical Composition of the Granites 



The following analyses f will give a fair idea of the ranges in com.posi- 

 tion of the granites which have been described above : 





I. 



II. 



III. 



IV. 



V. 



VI. 





Conanicut 

 island. 



Westerly 

 gray. 



Westerly 

 red. 



Millstone 

 point. 



Red Granite 



Company, 



Stony creek. 



Brooklyn 



quarry, 



Stony 



creek. 



SiOj 



TiOa 



71.23 



0.21 

 13.64 



1.70 \ 



1.00 / 



0.05 



2.31 



0.75 



3.79 



3.55 



71.64 



73.05 



68.40 



■72.73 



72.06 



A1A-- 



Fe^Oa 



FeO 



MnO 



CaO 



M^O 



K2O 



Na^O 



S 



15.66 

 . 2.34 



Tr. 



2.70 

 Tr. 

 5.6 

 1.578 



14.53 

 2.96 



Tr. 

 2.06 



Tr. 

 5.39 

 1.72 



15.75 



/ 2.972 

 1 0.649 

 Tr. 

 1.64 

 0.12 

 5.78 

 4.16 

 0.626 

 0.48 



i 16.95 



1.05 " 



Tr. 

 8.15 

 0.90 



14.83 

 1.28 

 0.64 



Tr. 

 1.20 

 0.13 

 5.64 

 4.3L 

 0.12 



H2O 



1.72 



0.482 



0.29 



0.22 



0.65 



Total 



Sp. gr 



99.95 

 2.69 



100.00 



100.00 



100.577 



100.00 



100.86 



*.J. F. Kemp in Transactions of the New Yorli Academy of Sciences, May 18, 189G, vol. xv, p. ISO. 

 fThe writer takes this opportunity to express his thanlvs to Doctors Love and Vulte for tlie above 

 analyses, vvhicla they have been so liind as to malie for him. 



