H. A. Miers — Quartz from North Carolina. 423 



The crystal is somewhat difficult of measurement on account 

 of the uneven nature of the principal rhombohedron faces, 

 and the usual horizontal striae and vertical reentrant angles 

 upon the prism. 



The faces — R of the figure are curved and only retain a 

 small plane surface near their right-hand edges which yields a 

 brilliant reflection belonging to — R. The prism faces g$ g a 

 make a reentrant angle of 0° 20£' but g a is inclined at 59° 59' 



to?. 



The indices of X and <# 2 can therefore be best fixed by 

 measuring the inclinations of these faces to g a g^ s and u / 

 care being taken to employ the right hand portion of 3R, since 

 this face has a vertical reentrant angle (indicated in the figure) 

 of 0° 16'. 



The form <P 1 has been observed by vom Rath on similar 

 crystals from this locality (Zeitschr. f. Krystallographie, xii, 

 453, Taf. viii, fig. 1) and has the symbol 



40.5.17 = -V 9 - P{i= 15.4.19-6 



established without any doubt by the following measurements : 



Measured. vom Rath. Calculated. 



BE:0 1 = 11° 9' 10°57'-10°50' 11° 8f 



s : 1 19 33 19 54—19 56 19 38| 



u: <P 1 3 51 3° 57 3 43 



g a \ 1 19 12 19 1 



g: <P 1 50 16 50 14 



The face 2 presents somewhat greater difficulty ; it yielded 

 the following measurements : 



_ Calculated for 

 * 2 = 23.5.10 <& 2 = 32.7.14 



8° 30|' 8° 34|' 



24 27 24 30£ 



5 441 5 43§ 



R 



$. 



s 



<P< 



u : 



*\ 



9a 











^ 



Measured. 



8° 



26' 



24 



25^ 



5 



57 



14 



4 



52 



18 



14 4i 13 58 



52 49^ 52 46 



The measurements suggest as the simplest symbol : 



<£ 2 = 23.5.10 = ^-Pff — 28.5.33.8 



With indices of such complexity, however, which seem to be 

 scarcely subject to the law of rationality it is important to 

 ascertain whether a slight change of the numbers will uot 

 bring the position of the face into harmony with others of the 

 rare trapezohedra of quartz. 



Now (P 2 lies almost in the same zone with s and two planes 

 recorded by Des Cloizeaux in his classic memoir on quartz 

 (pp. 107, 118) namely : 



