FELDSPAR DETERMINATIONS. 



Measurements of the entering angle on the 



basal cleavage plane. 



{Gfmiojncter.) 



Angle between tbi; principal sections of 

 adjacent hemitropic bands in sections 



cut parallel to O. 



(Angle between maximum extinctions.) 



(Z)es C/oiseaux's Method.) 



Angle between tbe principal sections 



of adjacent hemitropic bands in 



sections cut at random in tbe 



zone 0:il. 



{Des Cloiseaux^s MeOtod.) 



Lower zone of bed 22, Eagle R. Section . . . . 



Coarse-grained diabase, north of Delaware Mine 



Coarse-grained diabase, north of Delaware Mine, 



equiv. of bed &i 



f Entering angle on basal cleav- 

 age 



Lower zone of bed 94, Eagle R, Section . 



Coarse-grained diabase, west of Quincy Mine . 



Coarse-grained diabase, mouth of adit at the 



Daeotah Mine 



1' Angle measured O \ ii . . . 

 Same angle measured under 

 microscope 

 Another cr^'stal under micro- 

 scope \ li 



Bed 9S. Eagle K. Section; diabase. Feldspar 

 prehnitizea 



Bed 107 A , Eagle R, Section (light type), dia- 

 base. Feldspar prehnitized 



So-called Syenite. Granite St. Quarry, Somer- 

 viUe, Mass.: locality known for its prehnite. 

 Feldspar much altered to prehnite 



Lower zone of bed 87, Eagle R. Section. Diabase . 



Middle „ 



Bed 45, „ „ „ 



Lower zone of bed 66. „ „ ,, 



!-grained, hard diabase, Southside location . 

 Bed 106, Feldspar segregation. Diabase . . . 

 Bed 107 B., (dark type). Eagle R. Section. Diabase 

 ' ower zone of bed 108, Eagle R. Section. " The 



Greenstone." Meflaphyre 



Bed 90, Eagle River Section. Melaphyre . . . 

 Bed 64. (lower zone). Eagle R. Section. Melaphyre 

 Bed 05, under the " ash bed," Eagle R. Section. 



Diabase or diab. porphyry 



8th Bed, west of Pewabic, west conglomerate, 



St. Mary's location. Diabase or diab. porphyry 

 Bed 95, Eagle River Section. Diabase . . ". . 

 Light-colored diabase, " 800 ft. E. of Hungarian 



Lode " 



Bed 61 (lower zone), Eagle R. Section. Analcitic. 

 Diabase near Houghton ("y. bowld.") Feldspar, 

 changed to prehnite and chlorite ..... 

 Coarse-grained rock from Sec. 5, T, 47, R. 46, Mich. 

 Pseud 0- amygdaloid, 50 ft. west of Houghton 



conglomerate. Mesnard location 



= 50^— 173° 12' 

 93° 24' 

 93° 29' 

 90^ ±10' 



Alb. Olig. 

 Alb Olig. 



Extinction Angle ± 3^ 



172^ 09' — 172-^ 49' 



17IO30^_172 '21 



170'^ 54' — 171° 06' 



17P5K'~172°25' 



171'Ml'— 171^46' 



' Ext*n. angle, two-thirds i 



I is on one side in each } 23° 43° 



, instance ) 



Angle between line of I ..n p, no 

 : ext'n- and edge Oltl . ( f*" & 0° 



In other sets of bands 6^^ and 3° . 



Extinction angle 6° 54^ to 8°. . ) 

 Sect, oblique. Angle in one set [ 

 2 to 3 times as large as in other ) 



22« 23° 31° 33^ 33° 33° 36° 

 29° 30° 31° 31° 34° 37° 38° 41° 



Anorth. 

 Lab. Alb. 



43° 46° 48° 49° 55° . . 

 59° 62° 63° 66° 66° 78° . 



6° 7° 11° 13° 31° 45° 58° 

 1 20° 20° 27° 



16° 20° 41° 



10° 11° 24° 29° 39° 66° 57° 60° 



24° 26° 31° 32° . . . 



22° 23° 34° 36° .... 



26° 29° 34° 35° 36° 36° . 



21° 21° 24° 28° 31° 34° . . 



5° 15° 15° 28° 31° 35° . 



61° 66° 66"^ 68° 70° . . . 



11° 12° 18° 29° 31° 62° 64° 



16° 20° 30° 49° 60° 70° 76° 

 43° 43° 48° 49° 50° 55° 1 

 58° 60° 60° 63° m"" 70° I 



38° 49^ 57° 60° 62° 66° . 



47° 64° 67° 73° 74° . . . 



38° 55° 60° 



10° — 17^ and 13^ 



I 1 10° 19° 19° 20° 23° 23° I 

 , i 27° 28° 28° 29° ... ( 

 10° 17° 27° 42°43°48° 63°65' 



44° 61° 64° 77° ... . 



r Lab. 

 [•Lab 



Oligoclase. 

 Oligoclase. 



Lab. or An 

 Anorth. 



Alb. Olig. 



Alb Olig. 



Alb. or Oli^ 

 Alb. or Olig. 

 Alb. or Olig. 

 Anorth. 

 Lab. An 

 Anorth. 



2.73-2.75 

 2.91 

 2,93 



Alb. or Ol 

 Lab. An. 



Labradorite. 

 I Labradorite. 



Ub. or Olig. 



J Alb. or Olig 



j SiO- 46.32 ^-1 

 Alb. or Olig. 

 Alb. or Olig. 

 Alb. or Olig. 

 Anorthite. 

 Labradorite. 

 Anorthite. 



i Si02 50.20 %t 



orthite.' 

 Anorthite. 

 Anorthite. 



Lab. or Anorth. 



Alb. or Olig. 

 Labradorite. 



I In the rock. Whitney Gaol. L. Superior. 



