ELIZABETHTOWN AND PORT HENRY QUADR.\XGLES 3/ 



123 



Pyroxenic 



Pyroxenic ar.orthosite, Pyroxenic 



anorthosite, summit of anorthosite, 



Elizabeth- Mt White- Giant trail, 



town face Keene valleys 



^lagnetite i • 16 2-09 1-62 



Titanite lOO .99 



Calcite i-oo .80 



Kaolin 439 697 



Total 10014 100.54 100-90 



Light colored minerals 83 14 81 89 85.52 



Dark colored minerals 17 00 18-65 14 -48- 



Xo. I. Pyroxenic anorthosite from the Woolen ]\Iill. i mile west 

 of Elizabethtown. Analysis by W. F. Hillebrand in the laboratories- 

 of the United States Geological Survey. 



Xo. 2. Pyroxenic anorthosite summit of ]\It Vs'hit^face. Lake 

 Placid quadrangle. Analysis by George Steiger in the laboratories 

 of the United States Geological Survey. 



Xo. 3. Pyroxenic anorthosite, High fall,. Giant trail, ^It Marcy 

 quadrangle. x-\nalysis by C. A. Jouet. ^ Department of Chem- 

 istry, Columbia University. 



The analyses are arranged according to the decreasing percent- 

 ages of silica. As the recalculation shows, lower silica does not 

 necessarily imply higher percentages of the pyroxenic constituents 

 since no. 3, the lowest in silica, has the highest percentage of feld- 

 spar and the lowest of the dark mineral. Its feldspar is, however, 

 the most basic of all, being within the bytownite ranges. 



In the quantitative system all three fall within class II, Dosalane, 

 order 4, Germanase, rang 4, Docalcic, Hessase, subrang 3, Persodic 

 Hessose. 



Intermediate gabbros demonstrably later than the anorthosites 



Special interest attaches to the two members of this variety 

 which have afforded evidence of the relative periods of intrusion. 

 In the case first cited, the succession has been shown by included 

 masses ; in the second instance, the irruptive contact can be fol- 

 lowed for over a hundred yards in the rocky bed of a brook, for- 

 tunately in a ver}^ accessible locality. The two cases will be de- 

 scribed under locality names as the Split Rock falls, and the Woolen 

 Mill. 



Split Rock falls locality. In the valley of the Boquet river and 

 south of X^ew Russia there is an intrusive mass which covers 5 or 

 6 squar©. miles and which is distinct from the anorthosites of the 



