O. Andersen — Aventurine Feldspar. 399 



EXPLANATION OF PLATES. 



Plate I. 





Fig. 1 . Albite (aventurine feldspar) from Fisher Hill Mine. Thick sec- 

 tion after (001). Ordinary light. Magnified about 30 diameters. 



The vertically elongated patches are hematite lamellae arranged parallel to 

 (112), the long edges being projections on (001) parallel to a-axis. The 

 streaks running in the direction from lower left to upper right quadrant are 

 also hematite lamellae parallel to (112). 



Fig. 2. Albite (aventurine feldspar) from Fisher Hill Mine. Thick sec- 

 tion after (010). Ordinary light. Magnified about 30 diameters. 



The large patches are hematite lamellaB parallel to (010) ; horizontal streaks 

 lamellae parallel to (021). Streaks running from upper left to lower right 

 quadrant at small angle with horizontal are lamellae parallel to (112) and (112). 

 Streaks from upper left to lower _right at large angle with the horizontal are 

 lamellae parallel to (150) and (150) with the elongated edges parallel to the 



Plate TI. 



Fig. 1. Oligoclase (aventurine feldspar) from Kragero. Thick section 

 after (001). Ordinary light. Magnified about 30 diameters. 



Elongated patches running from upper left to lower right quadrant are 

 hematite lamellae parallel to (150). Other patches are chiefly lamellae 

 parallel to (112). 



Fig. 2. Oligoclase (aventurine feldspar) from Aamland. Thick section 

 after (001). Ordinary light. Magnified about 30 diameters. 



Chiefly hematite lamellae parallel to (112); some parallel to (112). The 

 variations in the outlines of the lamellae are distinctly seen. 



Plate III. 



Fig. 1. Oligoclase (aventurine feldspar) from Aamland. Thick section 

 after (001). Ordinary light. Magnified about 50 diameters. 



Hematite lamellae parallel to (112) showing various outlines. Near the 

 center two lamellae parallel to (150) running steeply from lower left to upper 

 right. 



Am. Jour. Sci. — Fourth Series, Vol. XL, No. 238. —October, 1915. 

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