APPENDIX TO PART VIII 



JGGIRINE-AUGITE CRYSTALS 



FROM A MICROSAN1DIN1TE OUT OF THE TRACHYTE 

 FROM MOUNT CJS, ROSS ISLAND 



(With Four Figures in the Text) 

 BY 



Miss F. COHEN, B.A., B.Sc. 



The crystals * are all very small, but distinctly prismatic in habit, with a squarish 

 cross- section — average measurements being roughly | by \ byl mm. in the direction of 

 the a, b, and c axes respectively. 



They are remarkably brittle and readily break into cleavage fragments. 



Although good faces were seen embedded in the rock, those crystals that could 

 be isolated were unsatisfactory for purposes of measurement — the faces being nearly 

 all corroded and the extremities of the crystals always more or less broken. 



Three crystals were examined, all of which possess the a and b pinacoids and the 

 m (110) prism. In all, m is by far the largest face and gives good readings. 



The mean angles of the observed forms are tabulated below along with the 

 theoretical values deduced from the calculated elements. 



Of these forms one crystalf possessed a, b, m, u, s, o, and z (Figs. 1 and 2), and another 

 only a, b, m, s, e (Figs. 3 and 4). 



* Vide Dr. Thompson's paper, ante. 



f The back of the crystal was broken so that other forms may have been present. 



ii 149 x 



