TIM-: MONOCLINIC SYSTEM 



127 



hemiorthodome of one face each, u/l(ni: oob: me), (hoi), (hoi), 

 (hoi), i hoi). Fig. 256. 



V. The ortho and basal pinacoids, from their relation to the axis 

 <>! >ymmetry, will each be represented by one face. 



FIG. 255. The Upper Umiclinodome. 



FIG. 256. The Upper Front Hemi- 

 orthodome, (hoi). 



The clinopinacoid will appear as in type 5 with two faces. 



Examples. A single mineral, clinohedrite, H 2 ZnCaSiO6, crys- 

 tallizes in this type. Fig. 257 is a combination of the plus and 

 minus hemipyramid, (111), 

 plus upper pyramid, (771), 

 plus upper pyramid, (161), 

 and the back hemiprism, (110) 

 as found on this mineral. 



Crystalline Elements 



In addition to the two axial 

 ratios, in the monoclinic sys- 

 tem the angle p is required to 

 fix the characteristics of any FlG - 257. - Combination of P (in), q(iii), 



, , e ,, f m(l 10), t(771),z(161) on Clinohedrite. 



crystal form. The angle is 



measured in the diametral plane, and in the plus octants ; its 



value is therefore always given as less than 90. It may br 



