126 Waring— Quartz from San Diego County, California. 



within. This twinning is also markedly shown at the junction 

 of the prism and pyramid faces, by the development on one 

 individual of the e (5051) face and on the other of the V (4041) 

 face. This twin has developed on_one member_ between the 

 m and z faces the x (6151), T (4041) and e (5051) faces, and 

 between m and r on the adjacent edge to the right, the x (6151) 



Group of quartz crystals from Pala and Rincon, 

 San Diego County, California. 



and e (5051) faces; while the other member has developed only 

 the T(4041) face. 



In figs. 3a, 3b and la, lb are given orthographic and clino- 

 graphic projections of the two crystals numbered 3 and 1 

 respectively in the group of crystals above, showing the relative 

 size and positions of the rare faces. 



Figs. 2 and 4 also are distinctly marked twins ; the one 

 shown by a joint or break along the prism face, the other by 

 a distinct difference in opacity of the two members. 



